Edit for clarity: I'm not asking why the Tankie/Anarchist grudge exist. I'm curious about what information sources - mentors, friends, books, TV, cultural osmosis, conveys that information to people. Where do individuals encounter this information and how does it become important to them. It's an anthropology question about a contemporary culture rather than a question about the history of leftism.
I've been thinking about this a bit lately. Newly minted Anarchists have to learn to hate Lenin and Stalin and whoever else they have a grudge against. They have to encounter some materials or teacher who teaches them "Yeah these guys, you have to hate these guys and it has to be super-personal like they kicked your dog. You have to be extremely angry about it and treat anyone who doesn't disavow them as though they're literally going to kill you."
Like there's some process of enculturation there, of being brought in to the culture of anarchism, and there's a process where anarchists learn this thing that all (most?) anarchists know and agree on.
Idk, just anthropology brain anthropologying. Cause like if someone or something didn't teach you this why would you care so much?
I consider myself to be something of an anarchist, if mostly aspirationally, and I think you've crystallized something I've had a hard time putting my finger on. All the irl self-described communists I've met, or even socialists for that matter, spend a lot more time concerned about theory than actually improving material conditions for those around them.
It's always the anarchists, even if they don't actually call themselves that, that are actually doing the thing.
I don't hate communists, our ultimate goals align, I might disagree with the path to get there at times, but we are aligned on outcomes.