I think he should look into CBT, or at least some kind of cognitive therapy, of the sort that helps people with PTSD and other issues where they have difficulty thinking about a subject rationally. Some exercises he can try himself are to think around particular women and why he doesn't see them as being the same, character-wise, as men. Bust through illogical reasoning and keep going. That's basically a very stripped-back DIY version of CBT, an actual psychologist would be able to help a lot more, but feel free to PM me if you want some more pointers/resources.