As soon as I find out that someone is sexist/homophobic/etc, my opinion of them goes way down. I think it's good that you're calling him out on his sexism -- maybe he'll learn something.

I can't help but think at some point he'll just get tired of arguing and cut off contact. I'm not going to stop being the Annoying Bitchy Feminist for anyone, but... I'd actually miss talking to him. :/

If he values you as a friend, then I think he would change his behaviour towards you (i.e. stop making sexist comments when you're around) even if he doesn't end up changing his attitude/beliefs.