Stuff like this often gets flagged off the front page, but usually it then just sits on page 2 for a while. This one is now down to page 5 (at only two hours old, with 200+ points).
Users often flag stories like this because of high-inflammation, low-information threads will plenty of flameage and little thought. We've turned off the flags here so the discussion can continue, but commenters should please take extra care to post civilly and substantively. We're here to think, not fight.
I think the real reason people dislike sexism discussions is because there's not a whole lot rational discussion to be had about it. If you try to make a point about a single aspect you might disagree with, you get shouted down as sympathizing with sexists. There's no winning and there's no minds to be changed.
I reject this assertion. I am certainly not sexist, but I flag stories like these because they belong on Reddit discussion forums. Hacker News should be for tech-related discussion, in my opinion.