I think homosexual men are perceived badly because the actual act that the majority of people's perception of two men having sex together would have to include anal penetration, and since males are considered the stronger and savager of the sexes, then the act of anal penetration in man/man sex is considered a violent act, one of the most violent acts you could perform upon a straight man. If a man is being violated in such a way and is enjoying it, then typically a straight male would not enjoy the idea, because he would have to think of himself in the same position to compare, and since he is straight he has problems with it.
On the flipside, as females are considered the gentler of the sexes, a female/female sexual act derives a softness and gentle act. Not to mention, males tend to perceive females as sexual objects - so what is better then one sexually attractive female then two sexually attractive females, who are also obviously aroused enough to perform sexual acts upon one another for (in a male's perspective) no obvious reason then to tittilate males, who would want nothing more but to join in - mostly, i think, because instinctually he'd have two females to impregnate instead of just one. I think this is also the reason why a lot of men who get rejected by women get upset and call them a 'dyke' or something derogatory - they feel bad for being rejected and have no option but to insult the woman for not fulfilling her genetic perogative as well as his feelings, the poor little boy.
I have no problem with gay relationships, but i physically feel revulsion when i think of two men having anal sex. Though, i always feel revulsion when i think of anal sex, so thats just me. I find it interesting, however, that there is typically a 'giver and a taker' in such a relationship - that is, there is normally one male who gives anal more then he takes it - or, as my friend puts it, he like to 'bat' more then he likes to 'catch'.