Former Stars and Stripes reporter and later Sixty Minutes commentator Andy Rooney said about Hitler; “The worst thing Hitler ever did was to prove for all time that any peace is not better than any war.”
And that is absolutely how the left sees it. It wasn't the industrialized slaughter of twelve million people in concentration camps, slave labor factories and deep trenches beside idyllic looking villages. It wasn't tracking down every Jew he could find to be part of that slaughter. It wasn't throwing almost the entire inhabited world into a massive war or destroying architectural artworks that were centuries old.
No to the Left Hitler's biggest evil was to make it less likely for future socialist takeovers to happen peacefully.
Do you recall the elitist twits who were repelled at Sadam and sons being vulgarians ... some noting that Hitler at least liked good art?