It's not half the human race. It's "the women who would participate in OSS development but aren't going to now because we do things they don't like". That is a fairly small number and, given current CS enrollment statistics, amounts to /maybe/ 10% of the current OSS developer base.
So, if we spent some enormous time and effort eradicating whatever these women consider "sexism" from all OSS projects everywhere, we'd get a 10% boost in developer numbers. We'd have to subtract from this all the men we lost because we either kicked them out for being "sexist", or they left because OSS development wasn't fun for them anymore.
I put "sexist" in quotes because it doesn't really matter whether the behavior is sexist or not based on any legal or reasonable definition of the term; all that matters is what these women consider sexist, which, importantly is likely to be a much more expansive definition. It might be impossible to reject a patch from a few female contributors -- for any reason -- without being called "sexist" by them. Since some patches need to be rejected, regardless of the gender of the contributor, we'd need to create some official definition of sexism and then have ways to try accusations. This administrative overhead would be an additional cost to be deducted from that 10% figure.
I don't doubt that there's some actual sexism in OSS. There are assholes everywhere. But, from a practical standpoint, sexism in OSS is, always has been, and always will be a complete non-issue. We're talking about volunteer groups, not companies with a legal obligation to pretend to care about this particular type of assholery, and these groups of volunteers have all naturally created behavioral standards that by and large work well for them. They'll expel the worst assholes without prodding, but most people learn when they are children that it is usually fairly easy to ignore assholes, so they'll let "productive assholes" stay on and just mentally killfile them. This is exactly the right response. Outside of groups like Debian that /enjoy/ doing everything with a tour-de-force, no one will ever care if a few whiners claim they're being discriminated against even though they're being invited to contribute with open arms -- just like everyone else -- and no one ever should.