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?
Yeah, I'd definitely say part of it for me was the unchecked assumption that "those" revolutionaries messed it up because they were cruel or stupid. As much as I looked up to the things they'd done, I looked down on them for their lack of "purity" and lack of democracy.
For me it took genuinely reflecting on my western chauvanistic attitudes, and meeting real communists in Cuba and having a legitimate conversation with them. Once I'd found out what a communist in an existing communist country was like, I'd realized they had the same drive as me, and were far more effective than me!