I think gender disparity in free software is definitely a symptom of a problem. The free software culture does not usually have a code of conduct, so as long as you provide code, nobody will care what kind of awful person you really are. Except that some people do care. Those will not feel welcome. My guess is that many women and some men are put off by the anti-social, sexist, insulting, and downright hostile behavior of a minority of the free software community.