Enjoying being pegged by a girl being gay or not depends on whats in your head I think. If you're fantasizing being a submissive little boy while the big man pegs you... thats some gay shit. If you're just like, wow thats a nice feeling and I enjoy you doing that with your big tits on my back you sweet female totally not gay person. Well, thats less gay.
It's obviously a bit of homophobia to say "no butt stuff ever because thats gay" but I'm the same way. Don't want my butt touched. The feeling just gives me the creeps. If thats homophobic, so what. I don't have to stick things in my ass to prove anything to anybody.