Once upon a time there was a reddit sub called chapotraphouse. It started as being centered on discussion of a leftish pro-Bernie podcast of the same name but quickly exploded in popularity and became more about general left politics discussion. Over time, especially after Bernie's defeat in 2016 it shifted more and more left. The sub became a specter haunting reddit, having over a hundred thousand users. Eventually because they tolerated too much talk of killing slave owners (Spez famously said he thought if the world went to shit he'd probably be one of the people in charge of the slaves rather than one himself) as well as other things like being anti-cop they were banned in a both-sides-bad move along with The_Donald by reddit admins right after Trump lost re-election. This was after being quarantined some months previous. After that they built a lifeboat site for their users to gather at, that site eventually came to be a lemmy instance and eventually even later a federated instance so they were one of the first instances.

It's a leftist lemmy instance. Nominally left-unity with rules against just launching hate tirades against anarchists or Marxists it in practice leans Marxist though has plenty of anarchists, democratic socialists, etc. It's strongly anti-imperialist so tends to align with Marxist, Marxist-Leninists more than many (but not all) western anarchist groups on global geopolitics. It has stances that many Marxist parties would take issue with however including communities around drug use (the site is banned in China) and certain ideological beefs not really worth listing out here. It is in other words it's own unique culture.

In addition to being a leftist instance its posters are aggressive. People on reddit constantly complained and worried about CTH brigading (whenever the discourse in a front-page sub shifted left people would say that chapo was doing that) and though organized brigading seemed infrequent compared to how often people suspected it*, many of its users were incredibly active posters and there were a lot of them. So it has a kind of shit-poster history. Whereas some instances would just ban someone or remove their comments, they'll spam images of a pig pooping on its balls at people they disagree with first. Their way of interacting with those they disagree with is very strident and at times could certainly be interpreted as rude, they're very blunt and don't tend to do civil discourse. They can be antagonistic to an extent though it's not like they're a harassment site that will follow around an enemy user for days outside of their own instance.

*(it did happen in as much as they posted links to comments and posts they disagreed with until the quarantine when they stopped doing that, BUT they were accused more often than they could possibly do so as most of the sub was not about making posts like that)

And it should be mentioned they did have strong policies against bigotry which were enforced. They also had a large trans community. So they weren't fascists. They were not reactionaries. They did not have a culture of hate for marginalized groups. I've certainly had unpleasant interactions with users of theirs but I've also had pleasant ones. Some of them come off as real assholes, many don't.