wow... digging up an oldy... but lets get some conversation going.
men... by nature, are suppose to be polygamous. Its an unfortunate part of our character. Granted, modern men (like modern women) should be allowed the right to look, but never go further. Afterall, we all have eyes, and some men/women are certainly more attractive then others. If my eyes catch some beautiful woman really showing off (not obscenely) why should it be illegal for me to look.. she spent alot of time and effort to look that good. Its doing her a favor for me to appreciate her beauty. But... I would be a total hypocrite if I got mad at my g/f for doing the same thing with a guy. And I'll be a man about it, I can admit when another guy is attractive. Its not gay, its honesty. She can admit when a girl is. Doesn't mean we want to go molest/have sex with that person. We're adults. Its natural.
Now, about the cheating... if a person can have their judgement swayed to give in to their carnal desires (or the cheatee is just that good to break down their defenses) then the cheater did something wrong. IMHO, man or woman, once a cheater, always a cheater. If it happens once, it certainly can again. I've been on the bad end of that (had an ex that cheated) and I never trusted her again. We still dated for a few years after, and I would always be super paranoid about her jumping on another guy. (she claims rape, i claim she was slutty... cuz she was) If you don't avoid the situation, your just as liable when it happens, because you could have avoided it. (not saying rape is ok, but she teased this guy alot... got drunk and passed out. NO PART of that exempts her from her actions. espicially cuz it all happened AT HIS APARTMENT, and she shouldn't have been there drunk and shouldn't have been a cocktease at work, for the few years they worked together)
anywho, i digress. Guys cheat, and its seen as manly. Girls cheat and its seen as slutty. Why? Like I said before, women are suppose to defend their relationship and nuture, not throw their body around. Guys are the ones who use females for sex.. not the other way around. (external anatomy vs internal) Its not the best reason, but its the best I got.
Personally, I hold both parties responsible, and see it as a negative for both, equally.