Actually I think the focus on gender is misleading. Excessively geeky environments repel non-geeks, whether male or female. The fact that this particularly results in repulsion of women is just due to geekiness being rarer among women.

Those who say "who cares if non-geeks are repelled" seem to be assuming geekiness and programming ability are strongly correlated, but in my experience they seem to be pretty orthogonal, at least for the type of geekiness which leads to putting up Star Trek posters.