First, we need to stem the losses of women in tech that happen due to the traditionally woman-hostile culture that has pervaded the industry for so long, and is only now beginning to recede. Women (and in fact all minority groups) get pushed out of the industry by hostile work environments. A specialized channel like this allows companies to say "We don't tolerate that, so come work for us." It allows them to tap a potentially huge labor force before it shrinks too much.

Second, markets like these offer a less stressful job search for marginalized groups, because they can have greater confidence that they won't get jerked around this time. It means that less women get so fed up that they quit, which means less time and effort is required to reach a critical mass where the momentum of women in tech begets more women in tech on its own.

This isn't about excluding men; it's about providing a more confidence-inducing hiring process for marginalized groups.