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.