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?
This is a main part for me. Most in the USA simply do not hear any defense of socialist countries, so they assume there isn't a defense. They're entirely evil places on their face devoid of any redeeming qualities and their people lack humanity. The base assumption around here is anyone living in a socialist country is doing so because they've been deceived or they're being forced, because there simply isn't any reason to have socialist political aims unless you're an evil dictator.
I broke out of that particular headspace when the Iraq War started, since that was probably the first instance where I realized there were clashing political interests that could not compromise. I saw that anti-war activists weren't being tricked or forced, rather, they had good reason to see things in a particular way.