Why are they needed? To counter genderism? If so, doesn't it seem self-defeating to try to outgrow our sexist prejudices by actively countering them?

If women have suffered discrimination in the software development community, we can all make an effort not to let it happen. But to create an institutionalized/organized effort towards countering prejudice is to strengthen it by latching on to it, rather than acknowledging it and letting it go.

EDIT: To clarify my point, I think we all need to be aware of not only genderism but unfounded prejudice in general, towards all human beings. An institution/organization or summer camp towards the equality of all seems to me a more equitable premise rather than a 'Girls-only' camp, which seems to be legitimate only because most of us are aware of the historical prejudices towards women.