So to some degree this is true; people can generally come to a consensus that certain things like slavery or genocide are deeply and inherently evil and that an

So to some degree this is true; people can generally come to a consensus that certain things like slavery or genocide are deeply and inherently evil and that any advocacy for these things is worthy of dismissal. It's not always right, though. Millions of people were killed in the various wars that broke out when Catholic Europe tried to "cancel" the "abhorrent" ideas of the Protestant Reformation. Perhaps you can think of this phenomenon as a type of social immune system. It turns out that actual immune systems aren't perfect. Allergies and autoimmune disorders exist. Immune systems will sometimes overreact to a pathogen, or react to something that's harmless but resembles a pathogen, or even attack vital organs that the body needs to survive. I think you can probably infer the relevant metaphors from here. But to provide one particular example: during the 1950's, American culture decided to "cancel" the "abhorrent" idea of communism. Actual spies working for Stalin were discovered and put to death and there was a lot of scared talk about even more spies being afoot. At one point, a bunch of screenwriters with memberships in the American Communist Party were fired and blacklisted from their professions. Ultimately, the climate of paranoia and fear resulted in personal ruin for more and more people as anticommunist demagogues went after as many of their perceived enemies as they could. There was a broad chilling effect; not only was it considered totally abhorrent and unthinkable to actually be any stripe of Marxist, but even saying, "hey, I think this is going a little too far" was enough to be branded a communist sympathizer. The only way anyone managed to criticize it was to write vague stories about literal witch hunts and pretend that they weren't allegorical. Clearly, this system isn't perfect. But neither do the excesses of McCarthyism actually excuse Stalin or the now-thoroughly-documented actual infiltration of Soviet spies and assets in 1950's America. It is possible to see the evil in both.