While HN tried and abandoned the "no politics" rule, it does have a soft "no partisan flamewars" rule and a vague "stay on topic" rule. It bans violators pretty effectively - if you're just starting trouble you won't last long.
Also, on HN, you can't reply to people, only to a comment. And it doesn't end up in any inbox. This makes it a lot harder to maintain a longstanding "beef"; we have to do that manually.
You can be on topic and only making calm, cited comments, but get shadowbanned for having sufficiently controversial views.
HN is like any other forum which censors certain views for being controversial.
Like stating that BLM is a Marxist organization — with a citation to their founders describing it as such.
HN relies on your belief that they only ban people “starting trouble” to remove certain topics from conversation, like how Marxist activists are using historic wrongs as a way to undermine society and for their own selfish enrichment.
Depending on your views, you can't directly say what you're thinking about certain topics at HN. You need to dance around the issue. Pose questions, give them rope and allow proponents of those ideals to provide their rationales. Once revealed, you can examine these topics.
Perhaps for those who haven't been down these rabbit holes repeatedly, it appears as assumption. The rationales you see may not have been provided explicitly or scrutinized. It can be a bit long-form and tedious, but it is part of assuming good faith.
Consider how your post above might appear to someone who takes an idealistic view of these activist movements. They might not be aware of the Marxist influences. Even if they are, they might genuinely believe that Marxist movements do not result in centralization of power. It is easy to overlook these points.
Also, on HN, you can't reply to people, only to a comment. And it doesn't end up in any inbox. This makes it a lot harder to maintain a longstanding "beef"; we have to do that manually.