Given that IME most women's eyes immediately glaze over when the word "computer" is mentioned, I doubt that "our community isn’t great at encouraging women contributors" is the reason why few women are in computing.
Given that all the women there had explicitly signed up to do programming, I doubt that any of them have eyes that glaze over at the mention of computers. Surprisingly for some people, there are variations among women just as there are variations among men. I'm pretty sure that most men also have no interest in computer programming. Finally: http://xkcd.com/385/
Which is probably why pwpwp didn't specifically refer to the self-selected women in the class, but made a general point about the industry and the ridiculous attempts to impose a completely artificial 50/50 gender ratio.
The comic could have just as easily said "one girl is good at math therefore exactly as many girls as boys are good at math."
While I agree a 50-50 gender ratio seems artificial at the moment, fact of the matter is the tech industry is becoming one of the great sources of power in society (think skynet). I think for the sake of civilization, we should try to involve women as much as we can and aim for the 50-50.
"I think for the sake of civilization, we should try to involve women as much as we can and aim for the 50-50."
I think for the sake of civilization, we should not try to aim for a 50/50 ratio. Your utopia is another person's dystopia. Not all of us share your morality.