I think it’s a couple of things
Western chauvinism inculcates “those are bad countries doing bad things in a bad system” which takes a lot to unlearn.
Authority can and always is abused for corruption and has been abused for corruption in communist systems, which in part justifies the charge that any system with structural authority will be abused for corruption.
Angst vibes lead to a “fuck every system” attitude.
By standing against all authority structures that actually exist or have existed, they are immune to criticisms based on reality, so I think to a degree it’s a stand you take when you want to take a stand but don’t want to accept that reality is always flawed.
Communist states are often militaristic which sits uncomfortably close to nationalism.
Calling bunch of football hooligans getting their shit kicked in “kristalnacht” is Holocaust denialism imo