Stalin was left wing. I second the recommendation for Stalin: History and Critique of a Black Legend. Losurdo uses near-exclusively western sources, including the Nazis, to counter the legend surrounding Stalin.

they are teaching that stalin is evil because he is rightwing?

Yes. That is essentially the lesson they derive from Animal Farm: that any communist/socialist revolution will ultimately devolve into "the same thing" or "just as bad" as fascist dictatorship. If you you don't recognize the incessant equating of Stalin with Hitler in both popular media and school curricula, then I don't know what to tell you. And when I say they derive that lesson from Animal Farm, that is not to let Orwell off the hook at all, because that is the most obvious and valid way to interpret it, as Orwell intended.

What's more, the lesson seems to be one you've absorbed and accepted, considering you're touting Animal Farm as if it has pedagogical merit instead of treating it as the silly, puerile rightist dreck that it is and even worse, insisting that fucking horseshoe theory is a useful heuristic. Oh and of course unironically using the epithet "tankie" to refer to other leftists in the same comment where you said you "just wish local efforts could connect to larger efforts, since we need multiple groups cooperating in solidarity, not isolated individualism" (and to be clear, that latter quote is good and correct but demonstrates unrecognized hypocrisy in someone who also talks about those ebil "tankies").

Any one of those things is enough to induce a huge facepalm in any leftist who has actually engaged with real leftist thought and theory. Yes, we are actually reading the words that you're typing and we can't help but wince.

Woah damn, sorry comrade I didn't even think of that!