Just because Jamal is black doesn't mean he's any worse/better/special than Henry who happens to be white. Just because Sally is a lesbian doesn't mean she's any worse/better/special than Cindy who is straight. You get the point.
Stop categorizing people. There are no categories. There are only people. All equal regardless of age, sex, sexual preference, "race", origin, religious beliefs, ... Only people. Equal people.
Yes, affirmative action makes a big assumption when it posits that a lack of diversity is caused by prejudice. But might that not be the case, that often a lack of diversity is caused by prejudice that can most easily be countered by a directly oppositional force? To be fair, it is this assumption that must be challenged when you challenge affirmative action.
Also, from what I understand in the FLOSS world, the number of contributors that are women are once again a smaller fraction than the number of software developers in general.
What I am saying is that due to reasons such as social selection, bias, expectations of what women should do, discrimination etc less women are interested in software.
As you said, women are less interested in software, they also in general are less interested in science and technical tools than men are, this is why we can observe so few women in tech. I have no idea why this is, it could be "expectations of what women should do" or maybe and I know that this sounds bad but it can't be ignored just because it doesn't sound good, a natural aversion in many women (not all!) for scientific matters or maybe a combination of both and more. I have absolutely no idea as neither reasons have been proven scientifically so I won't venture into any wild guess. But blaming it on white males imposed discrimination seems ridiculous and misses the point.
Development looks like a boys club from the outside. Changing that perception will require active effort from the inside. No one puts in the effort because "We aren't sexists! We love women! (We love women so much! [Please, women, come talk to us!])" Apparently liking women forgives being completely incapable of creating an inviting environ.
None of this comes as a big surprise to anyone who knows developers. Right leaning people who are overwhelmingly from privileged backgrounds and spend most of their time absorbed in a subculture that places pride in technical accomplishment above manners. This is not a group to expect a warm welcome from, especially if it means that they might have to tell less crude jokes, or take down some objectifying imagery.
But sure, it could be a natural aversion. That's a studied hypothesis with thousands of hours of research behind it showing...something, somewhere...right? The truth must be somewhere in the middle, I guess.
This is not a simple matter of people being actively or even passively discriminated against. This is the result of the environments, decisions, and treatment people receive from their earliest elementary school days; there is almost nothing that can be done by the time people are in college. I have watched EE and CS departments do everything imaginable to try to increase diversity, yet they have made extremely modest improvements.
Somewhere between the beginning of middle school and the end of high school, girls seem to stop being interested in math, science, and things that are relevant to engineering and CS. Somehow, my female classmates who had high scores on the AP calculus test all wound up somewhere other than engineering -- psychology, accounting, management, etc. Despite every possible opportunity being made available to women, despite departments running the gamut of things that could attract women, despite women representing a majority of students at many colleges, women continue to avoid engineering.
So don't say that women are not getting the chance to be engineers or computer scientists. Women have more chances than anyone else; they are choosing not to take advantage of those opportunities. Figure out why that is the case, and maybe you can actually do something to solve the problem.