This is from the Imdb trivia page:
Will Smith refused to actually kiss Anthony Michael Hall just before their kissing scene so a camera trick was used showing only the back of their heads. In an interview, Smith stated that Denzel Washington advised him not to kiss a man on-screen for it would harm his career. Smith stated that he regretted not going through with it saying "It was very immature on my part."
So I don't think he would fuck a butt.. If I misunderstood you and you're asking if the character he plays have sex with another man in the film, then the answer is I don't know, haven't seen it.
Good for him for admitting it was immature (and unprofessional as an actor, really). At the time, he wasn't an international superstar, so I can see why he would have been leery.
IIRC, that was a good movie.