John's problem isn't that women don't want him, it's that he doesn't want any women who might be willing to date him. He has the ol' "I refuse to join any club that would have me as a member!" problem. (I mean, that's also part of why I don't date, I don't want to inflict myself on anyone I respect enough to consider, I'm just self-aware about it.)

While he's wrong about women *only* wanting assholes, plenty of assholes *do* find plenty of dates, so while assholishness is definitely his wider problem, it's not why he can't find dates. The reason he can't find dates is that he's not willing to date the sort of women who would date a loser asshole. He has to fix one thing or the other. (The callback for "Girls only go for assholes" is always "You must be swimming in offers, then".)