Ok… Go look up Stalin’s purges and Mao’s “cultural revolution”.
No True Scotsman is a logical fallacy whereby a subset of a group is considered not a “true” member of a group because X.
Scott #1: No scotsman puts sugar in his porridge.
Scott #2: I put sugar in my porridge.
Scott #1: Well, no TRUE scotsman puts sugar in his porridge.
In this case, the argument will be made that the Chinese Communist Party (responsible for 50–80 million of murdered Chinese and which is still murdering people for their organs today) and the Communist Party of the Soviet Union (responsible for 30–40 million murdered Russians and Ukrainians) were not REAL socialists. (Even though socialism is at the core of both their ideologies.)