Dr Kathleen Richardson, a robotics expert at De Montfort University in Leicester, England, warns that sex robots could contribute to the systemic dehumanization of women and children....There is no reason to believe that users of sex robots will lose the distinction between the object they are objectifying and actual women (or children). If anything, this might provide an outlet for people of very strong but antisocial desires to express themselves without hurting real human beings.
“Technology is not neutral. It’s informed by class, race and gender. Political power informs the development of technology,” she told the Washington Post. “That’s why we can do something about it. These robots will contribute to more sexual exploitation.”
The real argument against this is not what it will do to the robots, but what it will do to the users. The problem isn't that they're using an appliance for its designed purpose, but that they're treating their own sexuality as a toy. This isn't a new problem: it applies to all such uses. Here's Kant on the subject, from The Metaphysics of Morals.
Kant can be a little opaque, and there's a lot more that has to be read to appreciate his full argument, but in sketch he is arguing this:
1) All things that happen have a cause.
2) For most things, that cause is something else acting on the thing being changed, e.g., sunlight hits ice, melting it.
3) These actions are not free, because they are caused by something else acting upon you.
4) Human beings, and other rational beings, have a possibility to act freely.
5) This only occurs when we are our own cause.
6) When we act as animals, we are not behaving freely: we are giving in to being acted upon by an outside stimulation.
7) Rather, we are free only when we reason to the right thing to do, and do that.
8) We can reason that the obvious good of sexuality is the preservation of the species.
9) Other uses are mere animal ends, and lack dignity because they lack freedom: we are throwing away our rational freedom and allowing ourselves to be driven like an animal.
10) Thus, dignity is only compatible with rationally electing to use sex for its proper purpose.
This is not a new argument even to Kant, although he frames it in what he would call 'pure practical reason.' You can find the same basic argument in Aquinas or Aristotle. It's an argument that has always struck me as incomplete: it's missing something, though after years of considering it I'm less sure than ever that I can say just what it is missing. Aquinas' version is better -- he distinguishes not one but three goods associated with sex -- but it doesn't avoid the conclusion that only this one mode of sexuality is fully good and worthy of a free and dignified human being.
Whether or not it's quite right, though, it's surely a good part right. Thus, the strong argument against sex robots isn't that they will lead to people imagining exploiting women or children: what is more likely is that those people are already imagining it, and might substitute the appliance for an actual person who would otherwise be exploited and harmed. The strong argument is that this mode of sexuality is itself necessarily harmful even to the user. It cannot be practiced without harm, even if in fact it reduces the actual incidence of harm to innocent third parties.
Kant makes an argument in the quoted passage that we can know this in part because the act is shameful. You're happy to present your spouse to the community, but would presumably hide the fact that you own a blow-up doll (or sexbot). I think he's right that it ought to be shameful, and that a decent society would be ashamed of such things and keep them private. What I wonder, though, is if a society is necessarily ashamed of it. Ours has come to think of free expression of sexuality as a kind of positive good, and might well treat parading your sexbot around as an act of courage. Can't you imagine hearing how "brave" someone was for "being open about his sexuality" in this way?
If that's right, then shame and reason have come apart: we aren't ashamed of what we ought to be, and have begun to praise vices as if they were virtues.
UPDATE: By the way, I've been doing some further reading on this subject, and the concept of "objectification" in sexuality seems to be rooted in feminist readings of Kant. Kant's talking about objectification in his sense, which is importantly different from the way these readings take him, here: the wrongdoer here is turning himself into an object by throwing away his rational capacities in favor of being acted-upon from outside. He gives up rational thought about what is right and wrong, and allows the impact of sensation to provoke desire, and desire to provoke action, as if he were a thoughtless object instead of a thinking subject.
Of course, part of what I think Kant gets wrong is the idea that even animals are "objects" in this way. The analysis may break quite early if, as seems likely to me, at least some animals are engaging in rational evaluation of desires or rationally adapting to ways of life compatible with other beings. There's probably also a basic error in assuming that rationality is divorced from sensuality, as both are emergent qualities from the world: to whatever degree we are actually rational, our ancestors had a potential for rationality that came to be realized in us. It is probably an error to think of reason as standing separate and alone, ordering reality rather than being ordered by it in the way that the Kant Song describes the First Critique. Reason itself is a product of the world, revealed by evolution, and its own function is therefore to be expected to be aligned with the world rather than divorced from it. We should expect to overcome Hume's objections not by Kant's apperception, but by a better understanding of the reality that we encounter with both reason and sensation.