I find that liberals are much more dismissive of US atrocities. Most communists I speak to know a wealth of details about the failings of mao and stalin.
Ask a US conservative about our 20th and 21st century atrocities - torture, massacres, coups, support for genocidal regimes and ecocidal companies, etc. - and they'll proudly defend our brutality. Ask a liberal and they'll hedge, deny and justify like an internet tankie who's never opened a history book.