They think you're either lying about wanting liberation for marginalized people, or that you'd entrust the task of liberation to a bunch of liars who would instead simply recreate capitalism but worse. They also believe you secretly harbor a suite of bigotries like transphobia or Islamophobia and you'd gladly endorse genocide against such groups so long as you had some vague aesthetic of socialist revolution. You're right that it's incoherent. None of what they're saying makes sense.

That's really the entire accusation. You're both brainwashed and insidious, you're dishonest, and you praise countries that are designated as "capitalism but worse somehow."

There's also a really serious element of nationalism that can't be ignored in the word "tankie." It means a westerner who is regarded as a traitor. You're praising foreign countries who are enemies of the west and that violates every other western political framework. Principled anarchists and communists get called tankies because we're the only westerners who wholly reject western hegemony.