Yup. Rummel has the facts DOWN. Socialism in all its flavors has killed more people than any other phenomenon—bar none.
Anything by David Horowitz will do. In Denial by Hynes and Khler does a great of job of exposing the the fundamental intellectual dishonesty and moral bankruptcy of those who continue to whitewash the crimes of communism if not actually applaud them! What's especially disheartening is that these moral monsters are almost all without exception firmly ensconced in our institutes of higher learning. Poisoning young minds since the Sixties.
The fact that they are largely unchallenged speaks volumes. It's a key part of the culture war that we've utterly and completely lost.