Guy on Guy= Majorly GAY... I have though wondered about people who like it in the butt from their girlfriend. I once worked with a guy that talked to me about his gf doing him in the butt with a strap-on and at the time I said he was definately bisexual. Now that I think about it, if you like it in the butt you like it in the butt. If you'd like a guy to do you in the butt then I'd say homo.
My gf used to always ask me about sticking a finger in my butt while blowing me. I once threw a knee to her head (accidentally) and she never tried again.
Way off topic, lol. But IMO a guy doing another guy from behind is gay. Imagine if you walked in on two men buttfudging, would you say that was gay lol.