I think it is to African-Americans, women, and other minorities. For example, broad stereotypes and criticisms are made, and frequently comments that say, for example, that racism is a problem, is voted down (my GP comment was voted down to -2, for example) and commonly harshly criticized. When those issues come up, most comments criticize any differing perspective before they are expressed. On the surface, there is very little interest in listening to other points of view - though I suspect that is the intent of the inflammatory commenters, to shut down discussion.

I think if you did a survey on HN users you would see that most of them think that racism is in fact a problem - that it is not good.

Also, I think its important to consider your comments holistically when seeing how they are received by the community. Of course you believe you comment communicates one thing, but in addition to that you have tone, other claims, and defenses. Any of which can result in a downvote.

I think these are great points, and the second paragraph, in some form, should be in the Guidelines. It's refreshing and encouraging to read them.

To be clear, I wasn't asking why that particular comment was downvoted; I'm talking about a much broader pattern.