In the throes of your rant at someone making a perfectly accurate observation you seemed to have made a false dichotomy.

The options aren't just that everyone on HN is sexist nor that women aren't interested in writing books on mind bending concepts, but another reason, as has been mentioned above, is that women for most of human history weren't allowed to write. From there it becomes rather obvious why there are less woman authors at all!

Also, check out some of Ursula Le Guin's work if you are into sci-fi.