Why can't they just disagree with the analogy? After all, analogies are inherently a comparison of two different things. People are prone to reaching for analogies as essentially just an insulting oversimplification, by pointing to something Very Bad (frequently a dramatic historical horror) and simply declaring that it is equivalent to whatever they're criticizing. Part of the allure is the positive feedback back-patting that frequently comes with it, without adding anything else (e.g. your reply, and the "insanely apt" reply from a now-banned account).

Regardless, it's destructive to reasoned discourse to treat people like enemies ("cognitive dissonance" is being used as an insult here) when the only thing you know is that they disagreed with you.

It's insanely apt and spot on. I'm going to be using it from now on.

He's being down-voted because it's whataboutism. It's no different than the 50 Cent Army that suddenly cares about Native Americans when the topic of the Uyghurs comes up. Yes, the red scare was bad, yes the US's treatment of indigenous people was bad. Everyone agrees about this. There's no school district in the US that uses a history textbook that says the Sioux deserved it and McCarthy had the right idea. The fact that similiar bad things happened in the past does not excuse them in the present. If anything it makes it more reprehensible that they happen today despite the example of what to do.