Hexbear.net is a Left-Unity instance populated mainly by Marxists and Anarchists. They generally don’t get along with Lemmy.world, whose admins defederated from the major Marxist-aligned instances.
Whether you block Hexbear is up to you, I enjoy my time there a lot but it’s also because I’m a Marxist. The ones saying they are “pretending” to be Leftist never seem to be able to explain why a large group of people would all ironically have theory reading groups and ironically support trans rights for years, even before federating with anyone else. What would they have to gain?
If I were you, I’d ask on an instance actually federated with them. You’ll get different perspectives than you will here, which is always the case when it comes to controversial topics like Marxism, where opinion varies greatly from instance to instance.
Do you have a link? Would be interested to see.