Dang's response came 4 days after the comment was written. Before being flagged, it was downvoted, but not to hell - it was gray, but still readable, like most of that poster's other comments. So I would say that someone may be justified in feeling somewhat attacked and not that well defended on such topics. As I said, it's a minority opinion, but it is somewhat tolerated.

Ideally, when someone claims that they can tell how smart someone is from how they look, that should be downvoted to oblivion and receive overwhelming counter-evidence or no attention at all.

Of course, what happened was quite OK, and much better than many other corners of the internet. But still, it's proof that that there is some explicit racism on HN, not just people not caring about others.