Some leaders inspired by communism committed atrocities. That doesn't mean I support atrocities. Karl Marx didn't command people to commit atrocities in his ideology, that's not really what the ideology is about. Communism is about creating a society where capitalists don't leech off the work of the workers and advancing to a stage where distribution can in the end be based on need.
Nazism, on the other hand, is an ideology that's specifically Hitler's invention which is centered around atrocities and purging people they don't like.