Assuming that whole instances are anti-anything is a great way to judge a whole swath of people quickly and look childish, it’s less useful to do anything else.
You only need to look at Lemmy.ca’s Hexbear refederation poll and compare it to Hexbear’s Lemmy.ca refederation poll. Lemmy.ca was overwhelmingly anti-Hexbear, while Hexbear was more reasonable and generally okay with refederating as long as Lemmy.ca understood that Hexbear hates landlords and whatnot. There are individuals on Lemmy.ca that are not necessarily anticommunist, but in aggregate Lemmy.ca is absolutely anticommunist, and the same applies to Lemmy.world.
Top comment from Hexbear:
as long as .ca understands nothing will fundamentally change from the hexbear population. I don’t think we should ever re-fed in bad faith or because it would be funny. If we know it won’t work, then we shouldn’t do it. But my hope here is that .ca has shed some of its former redditiness and is more willing to talk to non-liberals.
Top comment from Lemmy.ca:
its literally a troll instance. most instances defederated from them for a reason
As for your second paragraph:
No, Lemmy is just decentralized in nature, while that’s attractive to fringe left groups like hardcore communists, it’s also attractive to anarchists and fringe right groups like hardcore libertarians.
I restate, Lemmy is built on Communist principles. FOSS is anticapitalist in nature, hardcore libertarians prefer Reddit. Anarchists are also Leftists.