Great feedback, thank you for taking the time to respond so thoroughly. I appreciate it and even though I had realized the different approaches, I had not really compared their ideology to those levels. With your prompting, I have a better understanding and approach to my thinking about the subject.
You are right, evil is not something to be generalized into one single box. It has many faces and sometimes those faces are in direct competition for our destruction.
Hitler promised his followers a racially pure society that preserved class and social rank, Lenin and Stalin promised their followers an egalitarian, classless society. The fact that they both needed a totalitarian state, mass terror, and prison camps to achieve these aims was secondary, at least to them and their supporters.
So why would anyone expect a murderous dictator preaching class warfare, economic equality (in theory) and internationalism (at least in theory) to get along with a murderous dictator preaching the exact opposite?