When I was in 'girl mode', I noticed a lot of the same things. but when I hang out with my guy friends, they will point to another guy and say 'he's a douche' or something along those lines.
I think a lot of it is just how people are socialized to behave. I was always told that I had to behave in a certain way in order to establish my place in society and to keep my husband. Women are told that every other woman is out to get your man, your job, etc. Every man is told that he has to be this perfect representation of what 'man' means or he's not really a man.
I don't get it either. I am totally happy to just be myself and let others feel however they want. But I will say that when I was in girl mode I did feel that I had to fit into the sterotypical female role. Be jealous, be catty, be over the top in how I acted just so I could fit in. I can say that once I realized I didn't have to do those things I felt much better. I think it is probably the same thing for men. If you are not tough enough, strong enough, muscled enough then you don't really fit in. It's kind of sad really.