How would I, as a native born US Midwesterner, view the USSR or the PRC as "my own history"? Not to mention that the USSR and PRC have both transitioned from economic socialism to capitalism while retaining political totalitarianism. So maybe the economic system and the political system are separate issues? There are plenty of countries in western/northern Europe that are more socialist, and indeed more democratic, than the US.
It's kind of like asking contemporary Christians how they get away with not focusing on the Spanish Inquisition. Why would someone today view that as "their own horrific history"?
The real problem for the oppression and deaths is the totalitarianism, rather than whether it's coming from the left of right. Both left and right-wing dictatorship have the capacity and opportunity for incredible cruelty. Healthy human rights-respecting democracies do not, regardless of their economic policies. Although extreme poverty can also be deadly and could be considered a form of oppression. There are good reasons why workers in capitalist countries fought hard for workers' rights 100 years ago.
I've no idea what the Spanish inquisition has to do with the clear and obvious tendency towards an oppressive totalitarianism by left-wing movements throughout history.
I think you have to be willfully blind to deny this.
It's kind of like asking contemporary Christians how they get away with not focusing on the Spanish Inquisition. Why would someone today view that as "their own horrific history"?