[slg]

Would you say republicanism/democracy are immoral due to the slavery of pre-Civil War America?

That is the equivalent of what you are doing. You are blaming a theory of government for the crimes of a specific implementation of that theory. Genocide is not a central tenant of either fascism or communism anymore than slavery is a central tenant of republicanism, democracy, or capitalism. Fascism and communism are more authoritarian than other forms of government so they are both more attractive for people who seek totalitarian power, but that doesn't mean they are synonymous with the crimes of those totalitarians.

If Jones identified as a Stalinist, Maoist, or something similar I would definitely consider that more worrying as that is more similar to someone considering themselves a Nazi. Identifying as a general "communist" is not the same thing.