Seriously though, what are the most likely sources of his anti-female rage?

I used to think that it was an absolute fiend of a girlfriend, but he said that this was not the case. Now I think that he basically drowned in an internet echo-chamber. It's the same way women get radicalized into being feminists. They hear of all sorts of injustices and alleged injustices against womankind, and conclude that these are far more common than they actually are.

Or for that matter, Stormfags and their Jew-obsession. Go talk to any ordinary Jew, and he's no different from any other guy. But because of their overrepresentation among journalists, and quite bad ones at that, Stormfags convince themselves that da Joooz are out to get us.

He claims that his mother never physically, psychologically, or sexually abused him so the latter seems most likely.

His mother is a saint. But you're using this to attack him. Whether or not he has any trouble getting laid, and evidence suggests that he does not, that has no bearing at all on the validity of his claims.