The anarchist code of coduct says:
What is Unacceptable:
Degrading, disrespecting, or insulting another person or group of people, because of their :
[…]
- Political opinion
So, being a nazi is a political opinion. Denying the holocaust or thinking it should be done again is a political opinion. Thinking jewish people control the media and trans people aren’t real is a political opinion. Am I correct in gathering that it’s against the rules to disrespect someone for having these opinions? Is it against the rules to say “nazis suck”? Because I don’t like that.
Communism as an idea has no inherent connection to those atrocities.
“The criticism of religion ends with the doctrine that man is the supreme being for man. It ends, therefore, with the categorical imperative to overthrow all those conditions in which man is an abased, enslaved, abandoned, contemptible being.” - Karl Marx, Contribution to the Critique of Hegel’s Philosophy of Right
Fascism and Nazism on the other hand are ideologies of inequality and annihilation.
That is not to say that you can’t call yourself a communist and still be an enemy of humankind (so whatever kind of asshole) - but you don’t have to be. But once you are a fasicst, there can be no doubt that you are.