Why would they search specifically for "cancel culture"? It seems pretty obvious that the individual didn't search but instead took the time to try and find anything they could to make OP look bad.
Because it was immediately obvious from their post that they are engaged in political posturing rather than legitimate debate? It's really not hard to tell.
What you are describing is deeply, deeply pathological. You think people on HN of all places would do that? I mean I guess it is possible but shit man, I don't even know what to think about that.