The problem with Tankies is their authoritarianism and their “the enemy of my enemy is my friend” mentality. I could never support a movement that supports horrid dictatorships of any kind. Even as a socialist, I’d always defend a capitalist democracy against a communist dictatorship. If NATO defends a small democratic country against an invasion from its large and powerful neighbor, I’m all for it, even if I’d rather have a European military alliance instead of NATO.
It’s also absurd how they defend countries like China, which has perhaps one of the worst forms of capitalism, because they’re nominally communist.