With anonymous Internet comments you never know who's a real commie and who's a troll, but some of them are very convincing, and proud of it, and those are scary. I remember a conversation with one in YouTube comments. He seemed like a very friendly and reasonable "western European" type socialist at first. He tried to point out some of the "good things" that came out of the Soviet Union. However when confronted with the atrocities Stalin committed, he quickly shifted to deflection and lying to cover up the atrocities, then when pushed with evidence he asked for understanding: Stalin was overseeing a total conversion from a rural nation of farmers to a modern egalitarian industrial nation, and we can't judge him by today's standards. Under him "the soviets built great institutions of science and education, and employed millions of men and women".

When interrogated further, the commenter finally admitted that he thought that the millions killed in various massacres were "nothing but a statistic" and sometimes "people have to die for society to progress and move forward".

That polite leftist you're talking to, who claims they just want everyone to coexist and for the less privileged to be lifted up and given equity, is very likely an amoral sociopath.