Like, I've seen many smart people that are even, in theory, supporting of socialism and against imperialism who are well aware that there is a propaganda machine in the US and the west, who when it comes to anything about AES/past socialist states, they will just regurgitate state department propaganda without question.
Like, even if you bring up, for example, Xinjiang, and how virtually all evidence comes from some really bad research by a guy who clearly has an agenda, they will say something along the lines of "maybe that's true, but that doesn't disprove there's a genocide there". Which... is not how burden of proof works. Mind you, these are also people who clearly know about shifting of the burden of proof when it comes to climate change or evolution, but here? Then it's every logical fallacy, no critical thinking.
So what is it about these things that remove critical thinking from otherwise smart people?
There are so many pieces of anti-communist propaganda that do not make sense even if you were to trust them as facts. Like the Gulag Archipelago 11 minute applause story, they only make sense if you dehumanize their subjects. Dehumanization then makes additional propaganda more effective and even creates propaganda of its own.
Fighting propaganda is easy, you can just use your own propaganda. But fighting dehumanization is hard because you have to do it with rehumanization.