That comment was (a) not substantive, and (b) inflammatory. It was appropriate to downvote it. I'd guess it got more downvotes for being a (very) minority view than it otherwise would have, but that doesn't mean it didn't deserve them.
By "not substantive" I do not mean false, but rather that the signal-to-noise ratio of a comment containing many grand, unsupported claims is low.
Since you don't want to provide us with dozens of examples, how about picking, say, three that have the highest signal-noise ratio of the lot, and weren't uncivil? I'd like to see those. I know such comments exist, because I see them, yet the people charging HN with groupthink never seem to cite any clear examples.