This is totally expected, and typical of the sex-negative feminist type of reaction. Sex bots are the complete rendering of sexual objectification of women, women as nothing more than objects that a male is an owner of and can control, nothing more than a sexual tool for their pleasures. According to this idea, these kind of sexbots are teaching men how to treat real women, and this is obviously detrimental to women in the sense that we will have trained men into dealing with women as "bots", as "objects".
Now, one can be paranoid and think that what is going on here is the exact opposite, that it is a certain strain of feminists who are fearful of losing a certain kind of monopoly on being objects of desire. I suspect some of that might be going on in the subconscious of these people, but it is an undeterminate hypothesis, so let's leave it aside.
What should (always) be obvious (but never is) is that the above effect mentioned about diminishing the image of women is not the only side effect of this. What also happens (as it happened with porn, perhaps?) is that a lot of people's needs, some of whom otherwise would need to resort to violence or other insane means, will have been satisfied, and that is probably meaning that there will be a downward number of actual sexual violence towards women (as it has been happening for a decade or two now).
There's a certain aspect of the critique that is indeed interesting, namely, that there is a downward spiral towards meaninglessness in regards to sexuality with all these "tools" that we have or will have available. And that meaninglessness can indeed pervert the value we see between each other, increase the ways in which we stop caring or needing to be with each other, and instead resort to "relieve" ourselves with machines, tools, the internet, whatever. This wider effect can, indeed, devalue women themselves in the eyes of the users of these sexbots in this manner.
So there are these bigger points, but I gotta say, the nerve of these women trying to stop men from having a new "toy" for their own private pleasures is astounding. Can anyone imagine the reverse? Someone developing a manbot and a group of men's activists telling the scientists to stop researching that toy for women (and of course gays, but let's put that aside too, since the criticism has been heteronormative from the start) because that would "demean the value and image of men everywhere"? They would be ridiculed from every single roof top.
