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.

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

This is a reductionist explanation. The initial modern movement of socialists debated a lot on whether to support reform or revolution. Marx argued in favor of an authoritarian revolution after the failure of the Commune of Paris, but near the end of his life, he thought it was more sensible to seek out power through democratic means in societies with a liberal political framework, such as Britain. At this point, socialdemocratic parties still hadn't renounced to socialism - they just wanted to achieve it after democratically reaching power.

Through the start of the 20th century, there's a heavy rupture in the socialist movement when socialdemocratic parties begin moving away from the goal of actually achieving socialism, just at the USSR is born. This divide wider as the Cold War progresses, but we can still find a few important reformists who are aiming for a democratic form of socialism, such as Attlee in Britain and the French and Italian Communist Parties, although these two are, unfortunately, too loyal to the Soviet Union for their own good. As we enter the 21st century, socialist parties, for the most part, only want to tweak a few things about capitalism, but we can also find supporters of democratic socialism in the eurocommunist parties and the Communist Party of Japan. On the other fence, authoritarians who denominally support socialism, typically called tankies, tend to support the actions of whatever self-denominated communist regimes exist, such as China, and reject participation in liberal democracy.