The ones that I've had any negative interaction with in regards to anything related to politics have always quoted theory at me and told me that if I just read some theory, I'd agree with them.
I honestly haven't cared enough to see if theory actually agrees with them or if they're like those Christian extremists who believe that the Bible says to hate minorities.
Yeah, the creators of Lemmy are communists of some form (I don't remember exactly), and the older instances are largely groups of like-minded people, some egregious and some not. The most intolerable of the instances have been defederated from the rest of the instances, so they can't interact with the rest of Lemmy. ML is probably the most mild of the bunch and is largely just one of the big instances full of memes and such, but you'll occasionally see why they use the .ml address flare up in threads.