"People who built the Volkswagen, people who genocided millions of Ukrainians, what's the difference?"
Just thought I'd turn your line around. It's fun to reduce the atrocities of a movement to a good thing they did. Though the OP didn't even mention communists at all, he mentioned tankies, as in the people who actively deny the atrocities of stalinism and maoism. It's weird that you'd jump to defending communism.
You're right that there's a difference between fascists and tankies/ stalinists. And if this were a discussion in an academic setting, that might actually matter. But in an online discussion about the evils of both, it sort of doesn't really matter. They both have a track record of authoritarianism and mass genocides, and I don't get along well with people which defend either.
Almost the entirety of the political spectrum of most democratic countries sits as far away from Trump as it does from tankies. Let's stop pretending that if I oppose people who pretend that no genocides happened under Stalin I'm suddenly pro-Trump. There's an entire political spectrum between those two.