What is a gender-traitor, you ask? I am sure you all know a few of them. When you tell your co-worker to knock it off with the stupid sexist jokes, she is the one who leans over to exclaim "No, its really true. Women really are crazy drivers!" The dude bro you were talking to is now smugly satisfied that a woman defended his sexist bullshit, and she has earned herself a new friend as a result. I was that woman for a little while, and a lot of other women have been too.
She "doesn't get along with women". She watches porn. She calls men pussies as an insult. She gets to be the cool chick. Guys will say she isn't like other chicks, who act so fucking stupid and girly all the time. Nope, she is different. She isn't always whining or talking about boring girly crap like jewelery or babies. The gender traitor usually bonds with men over some typically masculine hobby like video games, guns, violent movies, drinking, etc. She gets to be an honorary dude, as long as she shrugs off sexism and helps dudes feel better about themselves. That is her job inside the group of friends.
She usually takes the job because she has very astutely noticed that things associated with women in our society are not as valued as the stuff associated with men. She has absorbed the belief that things like dominance (as in winning), violence, concealing feelings, and "toughness" are virtues from the culture. She usually doesn't identify with females in shows and books. She is spunky and doesn't want to resign herself to a woman's place, the way most women she knows will do at some point. Just being around feminine women kind of sucks, because they don't seem to understand how cool guy stuff is and how stupid girl stuff is. She doesn't seem to notice that none of the prized dude stuff is ever really available to her, not the way it is to fellow dudes. Dudes don't have to prove that they are the exception to the rule the way a woman does, nor are they treated as the representative of their sex at all times. A taste of dudely awesomeness is conditionally available to her if she continually denounces women in general. Her compliance to their ideas about female experience is the criteria used to judge if she gets to be an honorary dude. She won't ever really be one of the guys, and if asked directly they will probably tell her that. Her status as a potential sex dispenser makes it impossible for them to consider her a full member of the group the way a dude is. If she complains about sexism, they won't have to tell her, they can just ridicule her or shun her. Dudes will drop the cool chick from their group quickly if she makes them ask difficult questions about their behavior or attitudes. Allegiance to some feminine behaviors is acceptable as long as it proves something negative about women as a whole, or if it makes the cool chick more fuckable to her circle of dude friends.
These women show up to defend sexist men when other women have a problem with it. This piece from ERV is a nice illustration. She praises Dawkins for overcoming elevatorgate by providing childcare for a skeptic conference (something that men should do anyway), while deriding what skepchick does as worthless. He "won", unless you are too stupid to see that he totally won, because all interactions are considered a contest to a person who has internalized misogyny to this extent. I guess causing people to think and talk about their behaviors isn't worthwhile when you could be spending money? It is as though doing one thing to help women negates all bad behavior if you are richard dawkins, but if you are a woman who does something else you don't count at all. It may seem harsh to label ERV based on one event, but I am not. She consistently shows up to pharyngula or posts blogs to ridicule the idea that sexism exists and harms women, or that the actions of any specific man count as sexism. An army of dude bros show up to her blog to flatter her as a result or make comments about how she is the only woman with any sense in the debate.
The gender traitor, having prized toughness and dude defined coolness her whole life, has decided she is too cool or tough for sexism. She will overcome it and not even complain, its no big deal. If you complain about sexism around her she will tell you to just be like her and tough it out, and men tell women to be more like the cool chick when life is unfairly sexist. Sexism isn't a bigger deal than any other issue to overcome, right? Most women run into a really shitty sexist situation sometime in their life that they can't "win" at, it proves the gender traitor wrong through direct experience, and that is when things get complicated.
If she gets hit with an insurmountable sexist obstacle things can go one of two ways. She can either deny that anything is wrong or that sexism was involved (and her dude friends will enthusiastically help her find an excuse as to why it had nothing to do with sexism). Alternately, she can realize that things really are fucked up and no amount of any personality attribute will allow a woman totally overcome sexism. The latter requires that a woman tears down her whole identity. She invested it completely in masculinity as a virtue, and it didn't help at all when she was faced with an actual problem.
The way I am saying all this may make it seem as though the gender traitor is self-aware of what is going on, as if she says to herself "I will trade friendship for my respect of other women", but that isn't what is going on at all. She believes everything she says, she just doesn't pause to examine the troubling aspects of her behavior, or her "friends", long enough to notice the dynamic at work. That is why so many women do end up drawing the more difficult conclusion when being egregiously oppressed- they honestly talk about it with the dudes, and find out they will drop her in favor of some other more pleasing cool chick the second it becomes possible or just make fun of her until she shuts up. Some get weirdly angry over the mere suggestion of being wronged in a sexist fashion. She thought they were friends, but she was "the chick", not a friend the way the rest of the guys were. Bros before hos.