It's probably flagging, voting ring detection, or some moderator intervention (not sure if they can do more than killing or standard flagging).
I'd put my money on user flagging. There are lots of people here who have a knee-jerk negative reaction to anything that dares speak to the idea that women or black people tend to have a harder time getting VC/angel funding than their counterparts.
Hmmm... I'm not sure exactly how the voting ring stuff works, but I've heard that people can get tripped up by asking large numbers of, say, Twitter followers, to upvote them. I know the OP of the link in question, and I know he has a very large Twitter follower base. If he tweeted the link, it's not outside the realm of imagination that the subsequent voting pattern could have set off some anti-spam mechanism.
Of course this is all just speculation; but I think it would be wrong to rush to judgment and conclude that "HN is racist" because of this.
Yup, it happened to Yegg recently:
http://news.ycombinator.com/item?id=2203599
I think it would be wrong to rush to judgment and conclude that "HN is racist"
I agree, notwithstanding my previous point.