The "but he did it" defense doesn't work on HN, since people have to follow the rules whether someone else does or not.

But your flagged comment was obviously personally rude, and therefore much worse than what the other person posted. No matter how ridiculous someone's opinion is, if you can't comment civilly and substantively, please don't post here.

I agree with you about the article. In fact I was the moderator who boosted it (as described at https://news.ycombinator.com/item?id=11662380 and the links back from there.) But all that is secondary to the need to be civil, which the life of the community depends on.