Quite a number of feminist writers have discussed this issue. Helen E. Longino gives a precise articulation of the pro-censorship position, and I will rely primarily on her work as representative of the censorship arguments I wish to oppose.
Longino's position can be summarized as follows:
1. Pornography can be defined, in the words of the Commission on Obscenity and Pornography, as “  ...explicit representations of sexual behavior which have as a distinguishing characteristic the degrading and demeaning portrayal of the role and status of the human femaleas a mere sexual object to be exploited and manipulated sexually." 
Longino makes clear that this definition should be taken to apply to material "which represents or describes sexual behavior that is degrading or abusive to one or more of the participants in such a way as to endorse the degradation.”  Further characterizing pornography she adds, “Behavior that is degrading or abusive includes physical harm or abuse, and physical or psychological coercion. In addition, behavior which ignores or devalues the real interests, desires, and experiences of one or more participants in any way is degrading. Finally, that a person has chosen or consented to be harmed, abused, or subjected to coercion does not alter the degrading character of such behavior.” 
2. Pornography is immoral because it is harmful to women. Pornography is harmful first because it lies. Longino says, “Pornography lies when it says that our sexual life is or ought to be subordinate to the service of men, that our pleasure consists in pleasing men and not ourselves, and that we are depraved, that we are fit subjects for rape, bondage, torture, and murder.”  Pornography is thus immoral and harmful because it is libelous and defamatory.
Pornography also harms women because it supports the sexist objectification of women by men. It contributes to false, negative, and harmful images of women in the minds of men. Women's attitudes as well are warped by pornography, according to Longino. She says, “Women, too, are crippled by internalizing as self-images those that are presented to us by pornographers. Isolated from one another and with no source of support for an alternative view of female sexuality, we may not always find the strength to resist a message that dominates the common cultural media.”  Most importantly, Longino believes, pornography is immoral and harmful because there is a “connection” between the consumption of pornography and the commission of other acts of sexual violence against women. She says, “Contrary to the findings of the Commission on Obscenity and Pornography, a growing body of research is documenting (1) a correlation between exposure to representations of violence and the committing of violent acts generally, and (2) a correlation between exposure to pornographic materials and the committing of sexually abusive or violent acts against women. While more study is needed to establish precisely what the causal relations are, clearly so-called hard-core pornography is not innocent.”  Because pornography supports and reinforces the oppression and exploitation of women in these ways, Longino claims it is imperative that society not tolerate its production and distribution.
Before turning to the issue of censorship directly, let me first indicate the broad area of agreement I share with Longino concerning the nature of pornography and the undesirable effects of certain pornography on society in general. She is certainly correct in claiming that the feature which distinguishes pornographic (and immoral) depictions or descriptions of sexual behavior is the element of degradation. Erotica per se need carry no implication of degradation or of the endorsement of degradation. It is the addition of the element of degradation which both distinguishes pornography from the wider class of erotica and which makes pornography problematic.
The degradation is often explicit, involving portrayals of persons (men or women) in coercive and/or violent situations, portrayals in which the sexual subjugation and humiliation of one or more of the participants is central to the ideas communicated. Other degrading depictions are less explicit and grotesque, but undeniably degrading as well. Depictions of sexual behavior in which the pleasure or goals of some participants are treated as less worthy or important than those of others, or portrayals in which some participants are used, even consensually, as mere objects in the service of another's pleasure, are insidiously degrading and demeaning. They are degrading of human sexuality because they deny or undervalue the personhood of the persons portrayed.
Longino emphasizes how such portrayals degrade women, but it is important to note that they also degrade men. When men are portrayed as brutishly unconcerned with the pleasure, interests, or personhood of their sexual partners, their nature is degraded as well as that of their female partners. The image of men that much pornography puts forth is of people whose primary way of relating sexually involves brutal dominance, and concern with only the genitalia of their partners. This portrait of male sexuality ignores or denies entirely the capacity of men for tenderness and genuine, equal valuing of the personhood of their sexual partners. Women are degraded in pornography by being presented as fit objects for subjugation, rape, and abuse. Men are degraded by being pictured as brutes driven by desires to humiliate, subjugate, rape, and abuse women.
There are additional reasons to insist that the characterization of pornography be widened to include not just the degradation of women but of persons generally. Longino's characterization logically excludes the possibility of male homosexual pornography. If all the participants depicted are male, and a necessary condition for a portrayal's being pornographic is that it contain elements degrading to women, then no depiction which focuses exclusively on male homosexual conduct could count as pornographic. But many of the acts depicted which would clearly count as degrading if done to women (and therefore as pornographic) are also often included in male homosexual erotica. Depictions of coercive sexual violence, images of brutal subjugation, and the use of sexual partners as mere objects for the satisfaction of another are, unfortunately, at least as common in male homosexual erotica as in heterosexual pornography. Given that the degradation to which Longino correctly objects infects some homosexual erotica, as well as heterosexual depictions, it makes no sense to logically exclude all male homosexual erotica from being pornographic. Finally, though this is a relatively minor point, there is a sub-genre of heterosexual pornography in which the usual power relationships are reversed, and men are depicted as fit objects for humiliation, abuse, and violent subjugation by women.
One might still hold that pornography degrades only women by arguing that the power relationships that hold in society at large are so male-dominated that the treatment of men in these depictions as mere objects doesn't act to reinforce entrenched harmful attitudes and practices. In other words, depictions of men being treated in ways that would clearly count as degrading if done to women might not count as degrading because they would fail to have the same undesirable effects. This line of reasoning would be similar to that which holds that only whites can be racists, because blacks and members of other oppressed ethnic or racial minorities lack the power to act upon sentiments of racial hostility, while those in power, (i.e., whites) can and sometimes do act effectively to promote racist ideas.
But this reply would clearly not apply to male homosexual erotica, given that gay men clearly constitute an oppressed class of persons, persons whose sexuality has been pictured in a distorted way in the culture at large (as has female sexuality by the pornography to which Longino objects). Gay men as a class suffer disadvantages similar to those suffered by women as a class, in this case disadvantages related to the distorted stereotypical presentation of their sexuality.
Secondly, the reply speaks only to the purported effects of degrading depictions, and not to the issue of whether a depiction is intrinsically demeaning. One can grant that in general degrading depictions of women are more harmful to women (and to society in general) than those of men are to men (and to society in general) and still hold that pornography degrades men as well as women.
Let us turn to the issue of the harmful effects of pornography. The strongest claim made about the effects of pornography is that exposure to it causes violent or otherwise immoral behavior towards women. The issue of causality in human behavior is a vexed one in general, so we shouldn't be surprised if philosophical difficulties centering on free will and personal autonomy bedevil us in our specific consideration of pornography. There are layers of problems here. First, as Longino notes, the social science evidence concerning the putative negative effects of exposure to pornography is mixed. Further, most if not all of these studies deal with changes in expressed attitudes following exposure to pornography, and not with changes in behavior . The inference, on the basis of mixed and often contradictory results from social science concerning attitudinal changes after exposure to pornography, to the conclusion that pornography alters behavior is thus highly speculative, even if we accept the philosophical presuppositions about the causal nature of human behavior underlying much social science research.
The most difficult issues in assessing the claim that exposure to violence, or pornography causes substantive behavioral changes are precisely the vexed questions: (1) Whether human behavior is to be explained exclusively or even primarily causally; and (2) What is the nature of causal connection per se ? It is certainly not my intention to develop full answers to these questions here. But it is worth pointing out that the claim that human behavior is to be explained causally is, to say the least, philosophically tendentious. The conception of causality used in the kinds of social science research to which Longino refers amounts to nothing more than a formally specifiable relationship between independent and dependent variables in an experimental design. In such a design, if changes in the independent variable correspond with changes in the dependent variable, the relationship is said to be causal, provided that there are no hidden or intervening variables affecting our results; that is, provided that all behaviorally relevant variables have been controlled for . The manipulation of the independent variable is said to produce changes in the dependent variable. But the provision that all behaviorally relevant variables are controlled for merely refers us back to what I have already characterized as the philosophically tendentious assumption that what is behaviorally relevant, i.e., that what explains human behavior, is exclusively causal in the straightforward way in which chemical or physical changes are causal. This conception of causality in human action, from behaviorist psychology, makes no room for the possibility that autonomous judgment provided by consciousness intervenes crucially between the stimulus experience and changes in the independent variable. The simple causal model ignores the mediation of sensory stimulation by consciousness and rational judgment. If, as I would argue, judgment does intervene crucially between sensory input and resultant behavior in the sorts of cases under consideration, then the provision that all relevant intervening variables have been controlled for is necessarily unfulfilled. That is to say that no study of the sort to which Longino refers could possibly demonstrate a causal relationship between exposure to pornography and either attitudinal or behavioral change.
One important implication of this is that we are in some relevant sense responsible for our responses to exposure to such things as pornography, both in our attitudes and our behavior. If we pursue seriously the claim that exposure to pornography literally causes negative attitudinal or behavioral changes, we are dangerously close to absolving those with sexist attitudes and those who engage in sexual violence from responsibility for their actions. One is not usually held responsible for behavior one was caused to perform. If one is caused to perform some act, then one had no choice, no option other than to perform that act. Causes compel their effects. If we say that pornography causes sexist attitudes or behavior, how are we to answer the criminal who blames his attitudes or behavior on his prior exposure to pornography? Clearly people are responsible for any sexist attitudes they hold, and for their behavior. Longino's (appropriate) moral condemnation of sexism and sexual violence presumes moral responsibility, and moral responsibility is inconsistent with causality(at least with the notion of causality underlying the social science research she relies upon).
There is a second point to this metaphysical digression: regulation of expression has serious costs (a point I will take up later). Because of these costs, censorship shouldn't be undertaken lightly. We ought at least to have clear evidence of the means by which the speech or expression to be censored has the negative effects claimed for it. If we conceive of the negative influence of pornography in causal terms, this suggests remedies such as censorship. If a causal agent produces some undesirable effect, the most obvious solution is to eliminate that offending causal agent. If on the other hand, we conceive of the influence of pornography in terms of the persuasive power of speech, remedies other than censorship, such as counter-persuasion, suggest themselves. The burden of evidence lies heavily with those who support regulation of expression, and in the case at hand, the evidence of causal connection is simply too thin, speculative, and philosophically tendentious to support the prohibition of pornographic expression on causal grounds alone.
All this being said, it is crucial to acknowledge that in some philosophically less controversial sense, pornography as characterized by Longino is seriously harmful. But it is harmful in a more diffuse and indirect (but perhaps more insidious way) than Longino's language suggests. Like other kinds of speech and expression, pornography can persuade and influence. Even though the empirical evidence of harm is mixed at best, and even though metaphysical issues prevent us in any case from establishing a strictly causal relationship between exposure to pornography and behavior, it seems undeniable that the kinds of portrayals she discusses encourage, support, and disseminate degrading and demeaning attitudes towards women, and towards humans and human sexuality generally. This in itself is harmful and immoral, and therefore undesirable.
Further, many of the attitudes and ideas communicated by pornography coincide with sexist ideas in the general culture. Thus, the negative effects of pornography could be expected to be especially harmful because pornography acts to reinforce already embedded harmful ideas and attitudes.
Though our analyses differ slightly, Longino and I agree that (1) The distinguishing feature of pornography is its sexually degrading nature; and (2) That pornography thus characterized is immoral and seriously harmful. What I sharply disagree with Longino about is the appropriate response to this harm. Longino's position involves appeal to one version of the principle of harm: that actions which harm innocent others are immoral and therefore may (or ought) to be forbidden. But the principle of harm is false. It does not follow from the fact that a particular action is harmful to innocents that it may be justifiably forbidden. There are two primary objections to this principle. On consequentialist grounds, one might hold that a harmful action ought to be forbidden only if the prohibition of that act causes less harm than permitting it. On deontological grounds, one might hold that persons are entitled to perform certain harmful actions in virtue of rights they possess, quite independently of the harmful nature of the consequences.
On both sorts of grounds, Longino's argument for censorship of pornography fails. Let us consider the consequentialist argument against censorship first. Censorship of any sort carries with it the following risks and costs: 1) Regulation of speech tends to have a “chilling effect” on expression, especially if the boundaries of forbidden expression are vaguely drawn. This problem is particularly salient in this case, given the obvious difficulty in explicitly or operationally defining the key terms in Longino's (and my) characterization of pornography. What exactly would be forbidden if we prohibited “degrading”, “demeaning” depictions of women (or of human sexuality in general)? How could we hope to legislatively operationalize a prohibition against depictions of sexual subjugation? A key element of Longino's characterization is that pornography endorses the degradation depicted. How would such a determination be made in practice? Certainly there would be clear-cut cases, cases that would count as degrading if anything were to count as degrading, and cases in which the endorsement of the degradation could be uncontroversially read off the face of the depiction. But this characterization is so vague that the “gray area” between material patently degrading and that which is clearly not degrading is unworkably wide.
It is often the case that the point of view of significant artworks is purposefully ambiguous, or complex in ways that make a straightforward determination of whether the artwork “endorses” the degradation it depicts impossible. What is the point of view of David Lynch's Blue Velvet with respect to the violent sexual degradation it depicts? The intentional ambiguity of the film on this point (and others) creates a moral and aesthetic tension that form the basis of the intellectual interest of the work. Much the same is true of Stanley Kubrick's Eyes Wide Shut, a film which seeks to implicate the audience in its depiction of decadent degradation. Does the film have one point of view about sexual degradation, or several, in uncomfortable tension with one another?
It is a commonplace of jurisprudence that citizens have a right to know clearly what the law forbids. Under Longino's characterization we would have an unacceptably wide area of sincere and rationally defensible disagreement as to both the degrading character of portrayals and the point of view of those portrayals. (This objection has formed the basis of the judicial overthrow of local laws which proscribe the kinds of depictions to which Longino objects.) Longino's (correct) characterization fails radically to provide the precision needed for legislation, and I see no way in which her characterization could be modified to make it operationally acceptable without altering it essentially.
2) There is always a danger that once the principle of censorship is applied in one area that it will more easily be applied to another, and perhaps less desirable area of expression. This again applies with particular force in Longino's case. Why is it that she has singled out for protection a single class of persons (women) from a single sort of degrading depiction (sexual degradation)? Members of many groups are the targets of harmful degrading depictions in the culture at large: blacks, Jews, homosexuals, and so on. If women as a class are entitled to protection from these depictions by censorship, on what grounds could we allow speech degrading to other groups? To single out women as needing special protection from this sort of degrading material risks being patronizing to women by suggesting that women are weaker or more susceptible to damage than are members of other historically oppressed groups who have been subject to degrading depiction. Longino herself seems guilty of patronization when she claims that women are "crippled by internalizing as self-images those that are presented to us by pornographers."
And if the ground on which pornography is to be forbidden is not its sexual nature (and Longino carefully and correctly distinguishes her position from those who object to pornography on puritanical or prudish grounds, or on grounds that it offends modesty), what reasons would justify restricting only sexually degrading material? Wouldn't any degrading depiction of women be morally objectionable, and thus justifiably banned? Longino emphasizes that the degrading portrayals found in pornography are only one example of the demeaning view of women presented in the common cultural media, and that pornography derives much of its harmful influence precisely because it acts to reinforce already attitudes already present in the wider culture.
Using Longino's application of the principle of harm, it would follow that degrading depictions which caused the most harm would be those most justifiably prohibited. But it is reasonable to suppose that the damage done by pornography is actually less than by the more subtle and insidious degradations found in mainstream culture. First, those from the mainstream culture are more widely disseminated. Second, pornography carries a degree of social stigma, and an element of shamefulness and sleaziness. Thus, consumers or casual observers could be expected to be less affected by pornography than by the less blatant sexist portrayals more clearly endorsed by the wider culture. At the least, we have no evidence that pornographic portrayals are more harmful than nonpornographic but degrading depictions. And we have no evidence that degrading depictions of women are more harmful to women (or society in general) than degrading depictions of oppressed minorities defined by race, ethnicity, religion, or sexual orientation are to members of those groups.
If, in the name of consistent application of the principle of harm, we contemplate forbidding a wider class of speech than the sexual degradation of women, a class that would include all harmfully degrading depictions of women, and all harmfully degrading depictions of other disadvantaged or oppressed groups (or of humans generally), we seriously risk suppressing the vigorous exchange of ideas that freedom of expression is intended to insure. There are, for example, doctrines from various religions, including fundamentalist Christianity and varieties of Islam which explicitly endorse the subordination and subjugation of women, and others which demean homosexuals by characterizing their sexual behavior as wicked. These religious doctrines are false, I would assert, but nonetheless within the realm of appropriately protected speech. The same is true of numerous significant artworks and works of literature. Many of Pablo Picasso's paintings, such as Les Demoiselles d'Avignon , in which he depicts a group of prostitutes whose faces have been replaced by distorted and somewhat horrifying masks, endorse a clearly mysogynistic and degrading view of women. Picasso is only one of a number of artists notoriously unkind, even hostile to women, and I would argue that his distorted depictions present women as degraded (if frightening) sexual objects. Nevertheless, one could not seriously contemplate censoring the works of Picasso, or Christianity, or Islam.  The harm that would be done by such large-scale and vaguely defined rules of censorship would outweigh any harm attributable to pornography or other degrading material.
There are deontological objections to Longino's version of the principle of harm as well. Deontological rights theories assert that persons are entitled to the exercise of a range of liberties not because each such exercise has desirable social consequences, but rather because rights embody and acknowledge the dignity of treatment due autonomous rational agents.
Longino's arguments are strictly consequentialist. She makes no attempt to answer rights-based deontological objections to censorship. And she provides no argument for the priority of consequentialist ethical theory over deontological views.
There are feminist writers who argue for the censorship of pornography on deontological as well as consequentialist grounds. They argue that degrading pornographic depictions violate the rights of women. But on what basis other than the consequentialist arguments already considered could one make this claim? One would need to argue that as a matter of right , and not just as a matter of moral or social desirability, women as a group ought not be degraded by the speech of others.
I know of no way to justify the claim that women or members of other groups have a right not to be degraded in speech. I grant that if a successful argument for censorship of pornography or other degrading material were to be made it would be on deontological grounds. In the absence of such an argument, however, the case for censorship of pornography fails.
It is essential to note that though the argument for censorship fails, it does not follow that nothing should or can be done about the negative influence of pornography or other degrading material. Longino and other feminist writers are undoubtedly correct in the claim that degrading depictions, especially those of historically oppressed groups, exert potent harmful influences. Issues of the regulation of expression are important precisely because of the immense power of speech.
Though speech does not cause attitudes or behavior, it persuades and influences, sometimes in seriously harmful ways. What can legitimately be done to counteract the harmful influence of pornography? As is often said, the cure for bad speech is good speech. Those of us who are aware of the insidious influence of pornography can speak against it, and point out the harm wrought by degrading portrayals of women and members of other groups. We can educate others about the more insidious effects of non-pornographic but equally sexist depictions of women, as Longino and others have done. And we can exert our economic influence, and encourage others to do the same, on those who purvey degrading material. We can expect success in this just insofar as people are responsive to reason, just insofar as autonomous rational judgment intervenes and mediates between sensory input and resultant behavior.
[Note 2] 1 . Helen E. Longino. "Pornography, Oppression and Freedom: a Closer Look", in Laura Lederer, ed., Take Back the Night: Women on Pornography (New York: William Morrow, 1980).
[Note 3] 2. Ibid., p. 276.
[Note 4] 3. Ibid., p. 277.
[Note 5] 4. Ibid., p. 278.
[Note 6] 5. Ibid., p. 279.
[Note 7] 6. Ibid., p. 279.
[Note 8] In Longino's conception, what should we do with works like those of the Marquis Donatien-Alphonse-Francois de Sade, works which heartily and explicity endorse maximal sexual degradation of women? J. Roger Lee, in "Sadomasochism: An Ethical Analysis," reprinted in Philosophical Perspective on Love and Sex, Robert Stewart, ed (New York: Oxford University Press, 1995) presents a sophisticated and compelling argument that sadomasochism is unethical on Aristotelian grounds, and that it derives from and reflects narcissistic personality disorder, a deeply pathological condition. Nevertheless, de Sade's works, though they are a paradigm case of depiction and endorsement of sexual degradation, are clearly appropriately protected speech.