[dude with glasses in a communist t-shirt, arguing] I'm the only leftist here, your opinions are TRASH
[dude holding a theory book on smug, arguing] Read theory you losers, you're all WRONG
[dude in an anarchist hoodie, arguing] Nuh-uh, I'm the only leftist here, you're SHITLIBS
[the three dudes are now caught in a cartoon fight, glasses gone flying, punches everywhere, while a firing squad of nazis are targeting them with rifles]
[a confused nazi asks] Why… why are they still arguing?
Well you can either look at the now public soviet archives to see what the government was saying to themselves, you know primary sources, and plenty of historians who cite those or you can accept what anti-communists with no primary sources and a weird tendency to rehabilitate nazi-collaborators say.
Academics all over the world are in consensus about this, and you can be sure they've examined all the sources available to them. Tankies are the only ones who want to argue otherwise.