Stalin's Law 

Arguments defending communism (and to a lesser extent socialism) on the internet inevitably deflect from inherent and observable failures of both ideologies.

Deflections often (but not always) involve promises of absolute success in the next society they are inflicted upon, claiming that any service funded by taxation is an example of its success (conflation of tax with either ideology) or by downplaying truly awful historical events committed by communist regimes (e.g. the Holodomor). Other examples of deflection exist.

It is most frequently observed among people who have no experience of living under a communist regime. These people are often t-shirt communists.

Guy 1: "I know fascism is bad, but just look at the millions who have died under communist regimes"
Guy 2: "Nah man, real communism hasn't been tried. All those dictatorships were red fascism or were funded by the CIA. It'll definitely work in the next country it's tried in."
Guy 1: "Dude, that's literally Stalin's law. Stop defending brutal communist regimes"

Stalin's Law by Souper Rare January 6, 2022