Why do guys say so much awful things?
Guys posture and do macho things like this for the same reason that women are catty and say rude things about everyone behind their respective backs. To be honest with you those guys would probably consider themselves lucky to be having sex and would kiss that girl all over her ugly face, they just want to seem tough to each other. Watch the discovery channel or animal planet, men in groups behave very similarly to the way male animals do.
