Men are threatened by gay men. It's just tough guy masculine BS, macho culture, whatever you want to call it. It makes men uncomfortable, men are "supposed" to be tough, and "tough" men don't want to even accept the chance that they might enjoy a gay encounter...that's a threat to their whole identity, and for a hetero man to show approval of gay men (in hetero men's minds) there's a fear by many hetero men that this will make other people question their hetero-ness or masculinity. I feel bad for gay men, they're made to feel like they're lesser men by other men or even women sometimes.