So it's not even a socialist hugbox despite being a very strictly controlled socialist board, it's an identity politics hugbox. How this came to be, I have no idea.
Just the law of how crowds work. Socialists won't push you out for not being socialists, however identity politics people will push you out for not supporting their identity politics. The regular push and pull of discourse then changes where the fault lines lie. Socialist vs non-Socialist just isn't a fault-line that's being policed, so it becomes irrelevant compared to those hot-button topics.
EDIT: one way that those lines can change is because often emotional reasoning beats out factual reasoning. For example, if you went to such a socialist forum and start arguing in favor of free-market economy, they're not going to dispassionately argue against you based on economic theory, they're going to retort that the free market is a smokescreen to hold down black people and women and support the conservative status quo, all of which are appeals to emotion that end up leading to identity politics, because those arguments are
more effective at controlling the direction the discourse takes, than citing some more-factual analysis. Waving pitchforks to get rid of the wrongthinkers in our midst is always
more effective than reasonable discussion. It's not a good thing, but it's true.