Authoritarian communists. Think Stalinists, and people who support regimes like the CCP. The top left of the political compass.

Communists who glorify murderous regimes or dictators.

"I'm saying that, when a communist does it, it's not an atrocity."

If we wanted to mess up scansion for the sake of correctness, "when someone who calls themselves a communist."

Wikipedia has a good article on this. Basically authoritarian "ends justify the means" leftists. https://en.wikipedia.org/wiki/Tankie

Tankie is a pejorative label for communists, particularly Stalinists, who support the authoritarian tendencies of Marxism–Leninism or, more generally, authoritarian states associated with Marxism–Leninism in history. It is commonly used by libertarian socialists and left communists to criticize Leninists, although the term has seen increasing use by liberals and other non-leftists as well.

The term "tankie" was originally used by dissident Marxist–Leninists to describe members of the Communist Party of Great Britain (CPGB) who followed the party line of the Communist Party of the Soviet Union (CPSU). Specifically, it was used to distinguish party members who spoke out in defense of the Soviet use of tanks to crush the Hungarian Revolution of 1956 and the 1968 Prague Spring uprising, or who more broadly adhered to pro-Soviet positions.[5][6]

The term is also used to describe people who endorse, defend, or deny the crimes committed by communist leaders such as Vladimir Lenin,[7][8] Joseph Stalin, Mao Zedong, Pol Pot, and Kim il-Sung. In modern times, the term is used across the political spectrum to describe those who have a bias in favor of authoritarian states with a leftist legacy, such as the People's Republic of China, the Syrian Arab Republic, and the Democratic People's Republic of Korea. Additionally, tankies have a tendency to support non-socialist states if they are opposed to the United States and the Western world in general, regardless of ideology.[4][9]

Stalinists

Communist philosophy has a lot of really useful analytical tools. It describes and criticizes society, especially capitalist society, in a very sharp and insightful way. People should read and learn it because it's interesting, useful stuff that is easily applied to modern politics.

Communist philosophy also calls for a (typically violent) revolution involving an authoritarian transition to get rid of capitalist society and usher in the future collective state. When a violent revolution is being called for in (mostly) functional democracies, that should usher in some skepticism from a normal, reasonable person.

The tankies reallllllly seem to like the violence, though, and are extremely supportive of any state that claims to be communist regardless of what atrocities that state commits along the way. They will be intensely defensive against any criticism (criticisms like "maybe Stalin shouldn't have starved millions of people to death through incompetence and genocidal inclinations", "maybe Mao shouldn't have wiped out all the doctors and artists", "maybe Putin shouldn't be allowed to try and annex Ukraine", etc.).

At some point, it becomes hard to properly separate these supposedly "authoritarian left" types from the "authoritarian right" fascists. Political compasses are stupid anyway.