So you’re saying the CCP was a fascist party?

No, the CPC (the way to say the communist party of China without any racist baggage, which you probably didn't know about but you know now) made a very bad policy decision without very much intelligence about Pol Pot and while trying to stay on the good side of the US because they were very vulnerable.

I’m not sure how someone could respond to you when your response to sources was just rejecting them. I can show you non-Wikipedia sources, but I can only imagine college history curriculum would cause you to respond with accusations of propaganda.

Pol pot was not a communist. You aren't going to find any sources indicating that his policies followed communist ideas, youre just going to find sources repeating his claim that he was a communist. And people who haven't studied what communists actually believe or what policies they implement do not have the knowledge to discern further. People know less about Pol Pot than they do about Hitler but this is the same genre of "The nazis were actually socialists" which can be disproven by knowing what socialists believe and knowing nazi policy and comparing the two.

I can find it reasonable for a person looking at the available evidence to conclude that some communist regimes have committed massive atrocities.

Yes, at a similar level to any ideology that has been in control of a state will. States always produce excesses.

You might disagree, but how is that not (similar to your take on the other guy) soft holocaust denial?

Equating much lesser atrocities to the holocaust minimizes how bad the holocaust was and has historically been used to rehabilitate nazi collaborators and their movements in Eastern Europe. If you're unfamiliar now is the time to research Jewish scholars writing on the "dual genocide myth". "The line goes, with some variation "sure he fought with the nazis but only to liberate his country from the soviets!"

Communism as policy platform generally involves a window of authoritarian rule

A revolution is the most authoritarian thing in the world. It is one class, the proletariat, enforcing their will on another, the bourgeoisie, through physical force. Please read "on authority" and "state and revolution"

that is sometimes a bit difficult to distinguish from fascism (yes, there’s some big ones if you know what to look for).

Please consider that it is only difficult if you dont know a lot about fascism and communism and the waters have been made intentionally murky. (See dual genocide theory) The difference is night and day once you've read some basic analysis of the two systems.

And no Communism has ever reached such a late stage they were able to lighten up on the authoritarian side.

States exercise authority, and you'll always get excesses from them. The difference between proletarian democracy and bourgeois democracy is that in the former, the proletariat controls the democracy, and in the latter, the bourgeoisie controls the democracy. Socialist States aren't perfect, but the authority they wield is more aligned with the interests of the proletariat than under a capitalist government. States are required to protect a socialist society while capitalist empires still exist. When they no longer have external threats, the state should wither away, and if it doesn't, it will be easier to subvert by the will of the people given how the state functions and derives its authority.