I think this is the real cause and saying that he has aspergers or is psychotic or something is not only offensive but allows us to avoid facing up to what is a serious problem here, it allows us to put this person in a box marked 'nutter' and forget society's role in making him what he is.
He's just a nutter, his decisions weren't at all shaped by the view that he's got a right to sex, or a culture of misogyny that makes those views acceptable. Its like the whole thing with rape jokes etc helping rapists to get away with it, because this culture helps to legitimize it and make rapists think they can just get away with it because these views are partially acceptable anyway. What about someone like Frazier Glenn Miller or George Zimmerman, do we just say they are mentally ill and that's that? There was plainly nothing wrong with them, the main issue is a society and social setting that legitimized racism and antisemitism and helped Zimmerman for example kill a black kid for walking past and get away with it, mental illness doesn't come in and if you pathologize stuff like this you just end up missing the bigger picture IMO.