I’m sorry, #notruescotsman? Please explain?
Also, I’m going to have to disagree with you there. Plenty of other peoples have been responsible for far more deaths than any of the isms.
Among them Caucasian slavers and masters, as well as Middle Eastern and some African societies of old. And back then it was considered more or less acceptable by everyone who were not caught in that predicament themselves.
Socialism is bad, but I can’t imagine it was ever “20–40 millions of dead people for no good reason”-bad.