They are hardline Marxist-Leninists, something that is very rare in the western world even amongst those who identify as leftist or socialist. If their views make you uncomfortable, then you're not a ML, which is okay.
Left-wing politics is a very broad spectrum, and a lot of Lemmy users lean towards the more moderate end which brings them into conflict with the more radical communities that are Lemmygrad and Hexbear.
That's all there is to it.