Because America’s tortured history is wound tightly around the twisted bowel of race rather than class hatred, and because we fought and beat the Nazis and not the Soviets at great cost of blood, and because we are a revolutionary nation like the Soviet Union, our elites have never really taken seriously the fact that Communism was responsible for vastly more slaughter than Hitler, which is saying something. All the time I was growing up, opposition to Communism was treated as a sort of silly jingoism and Commies were treated like bogeymen. All you have to do is watch MASH reruns to get the atmosphere of how Enlightened People regarded those who thought Communism evil. All such ninnies were Frank Burns and Col. Flagg.
And it remains to be seen if post-Christian western culture manages to beat it in terms of body counts. But we are giving it a college try. And we are moving far and fast in imitating it as a police state too. Not hard to do once you decide that human rights come not from God (how passe!) but from the generosity of the state.