As the article link here mentions, I do not believe that most Amercian liberals envision a truly socialist/communist state. But I think they are naive.
The extensive attention paid to the Nazi crimes has helped sensitize people to the dangers of racism, anti-Semitism, and extreme nationalism. These evils have not disappeared. But at least the need to oppose them is widely accepted throughout the democratic world. A similar focus on communist crimes might increase recognition of the dangers created by ideologies based on class warfare and socialism (by which I mean full-blown state domination of the economy, not merely government regulation of private industry or a welfare state).
And the constant use of the Us vs. Them, Rich vs. Poor, Victim vs. Oppressor, Black vs. White, the list could go on and on…has created an class of useful idiot. Mobs are by nature very uncontrollable.
Of course, the combination of class warfare and socialism doesn’t inevitably lead to mass murder on the scale committed in the USSR, China, and Cambodia. However, they do greatly increase its likelihood. Almost every fully socialist government (by which, again, I mean a government that manage to take control over the vast bulk of the economy) that held on to power for more than a few years ended up murdering a substantial fraction of its population (usually at least 1–2%).
Read the rest over at the Volkh Conspiracy. We need to start reminding “them” every chance we get.