You are correct that there’s overlap of users with lemmy.ml, but I don’t see much of the offensive content coming from there. If nothing else, they put their masks on when on that instance. I’m sure there are people on EH with alts elsewhere, but they aren’t given the free reign to cause the same problems.
Lemmy.ml is no longer a recommended instance, and probably won’t be again. But yes, I agree with you that the confusion caused by defederation is a bad thing.
Does some of them being tankies have an effect on the code?