It sounds like you think history ought to be simple and it sounds like you think people’s political views ought to be simple. The reality is that everything is more nuanced, and it takes time and energy to understand. A lot of people, probably people similar to you, don’t want to spend that time and energy. But here you are, so perhaps you are willing to give it a whirl.
To begin with, the enemy of your enemy might not be your friend. Just because the USSR fought against Nazi Germany doesn’t mean that the USSR was run by people that we’d like to have lunch with.
And then it’s important not to think that the USSR in the early 40s is the same as what it was in the late 80s. Countries change over time.
It looks like you want people to hold very strong positions. “Communism is entirely good/bad.” “The US loves freedom.” “Marx is bad.” … In reality, political leaders are smart, and they’re very good at manipulating people who have simplistic absolutist views such as these. It is necessary to pay attention to the details.
And finally, even if I have some very strong belief, if I tried to push it dogmatically on to other people on the internet then they will just block me. It’s often a better strategy to try to discuss things and assume or hope that the other person is going to use their brain, just as you are willing to use yours.
Of course there’s no reaching some folks, and some people are just here to troll, but that’s nothing new and nothing to write home about.