It's only a problem if you don't like having chauvinism and western state propaganda brainworms questioned. As a ND queer communist I have never felt more comfortable and welcome posting than on hexbear. Their mutual aid comm is highly active and an immensely helpful place for many people. It's an adorable community, they get a bad rap by people that come in arguing in bad faith who then run away to shame the hateful 'tankies' on their main instance like this post here.
Their users are needlessly hostile towards anyone who disagrees with them, they had a bug that caused their emotes to become oversized on Lemmy which quickly flooded threads when their users spam them, and they have a reputation for brigading threads to "dunk" on people. They also really like to flood threads with graphic images of pigs shitting on their own testicles, because that's definitely what normal people do.
It's worth noting that they don't federate with other instances to participate in good faith, they do so in order to dunk on people and "dismantle Western propaganda" and "plant the beans of truth in other instances fields" and in general act in bad faith. Worse, their instance admins did little to stop this.
They were defederated from many instances for good reason, as their behaviour drove away a lot of new users. A lot of Hexbear users have alts on lemmy.ml and midwest.social, so the defederation doesn't stop their users from continuing to be dickheads.
And if you'd like some receipts, I have plenty of examples. Best viewed from an instance that federates with Hexbear, so you can see their behaviour for yourself.
Have you ever been around a child who gets some silly factoid in their head, but it's completely wrong because children are still learning the very basics of synthesizing the observable world into coherent ideas?
Hexbears are like children who have spent the last six hours explaining to you over and over again that cows can breathe under water.
Most of them are tankies (dumb political ideology) but most people took issue with the fact that they were the most annoying people on Lemmy. Every thread they'd be in would be a collection of the worst takes imaginable and they liked to start arguments with everyone else
"Tankie" is a caricature. The idea of a tankie is the ideal vision of a McCarthyian Communist. In reality, the overwhelming majority of people labeled as such don't actually fit that label, it's more of a way to cast an image of someone's positions based on, say, support for AES countries, and twist that into the evil Commie Pinko that haunts the dreams of 1960s children in the US.
So, yes, it's a pejorative, and not one I think is aiding leftists trying to understand the views of others. More often than not it's used as "commie" was: to shut down conversation and otherize people.