A few years ago I realized something about anime clubs: they don't like showing anime aimed at women. It's assumed that all the members will enjoy something made for men, such as the Gundam animes and anything with big boobs and lots of pantyshots. But god forbid we watch Pani Poni Dash, or anything where the protagonist and most of the leading cast is female - because the guys won't want to watch that. Or in one case, there's one guy who does, but we don't want to "give him power" so regardless of how many women want to watch it, we need to keep it out of the lineup just to spite that one guy.
First of all, it's just not true. Look at Miyazaki's famous movies, such as Spirited Away, Ponyo, and Howl's Moving Castle. Yes, most of his movies show a man being in power over the protagonist, but the protagonist in those movies above is female, and those are just three examples. Not to mention, my club watched Angelic Layer last summer, which is a pretty female dominated series with a few guys in the supporting cast, and the president did acknowledge that people enjoyed it. So now that he's acknowledged that, I have to wonder if he'll consider more series aimed at women.
The problem is that female nerds are assumed, if not outright expected, to be tomboys. We're supposed to like guys' anime, we're supposed to think giant robots and gratuitous violence are awesome, we're supposed to think pantyshots and tentacle rape are hilarious. For a female nerd to be accepted into the social realm of nerd culture, she needs to be one of the guys. If you're feminine, you may enter the group as a girlfriend, but be prepared to lose that status and any friends that came with it when the relationship is over, especially if you're unable to just laugh off a devastating breakup and move on the next day.
Raunch culture does run rampant within nerd culture, and the easiest way for female nerds to gain power and respect is to act like guys. Why? Because acting like a guy is empowering, while acting like a woman is degrading - because merely being a woman means having less power.
That's not to say some femininity isn't appreciated. If a female anime nerd cleans up well for formal events, bakes cookies, or can sew a good cosplay, she's definitely praised. And it helps to be pretty - just not too conventionally gorgeous. The problem is that if a girl is too feminine, she isn't taken seriously as a "real nerd," because being feminine and being nerdy are believed by many to be mutually exclusive.
The fact is, nerd culture is a boys' club. Anime conventions provide a slew of sexual programming, which is dominated by degrading sexual acts, if not outright rape (it may be animated, but it's still telling when a room full of people, men and women, roar with laughter as a high school girl is raped by her math teacher). Female gamers are still harassed in live gaming situations; to many of them, being ordered to "go back to the kitchen" is a common occurrence, and one she had better either find hilarious or stop playing. Female gamers often choose to play as guys to avoid the harassment. Men still dominate science, engineering, and computer-related majors in most colleges, and the few women with the guts to pursue such subjects often feel uncomfortable in the classroom, surrounded by men, practically hearing them wonder if she's in the right place.
Does anyone wonder why women are vastly outnumbered by their male peers in anime clubs and nerd conventions? Nerd culture is, for the most part, still a hostile environment for many women who'd rather stay home and watch anime, play video games offline, or remain in the server room about their nerd status.