"Youtube censors antivax content" is a true statement. It is not state censorship, but censorship nonetheless. Good thing / bad thing, for Youtube / for society at large, short term / long term, we can argue that. But let's get our facts & terminology straight.

This is semantics. In this case HN is censoring opinions right now through its moderation. Every forum on the internet censors. Your spam filter blocks others speech from reaching you etc.

While HN would kindly steer us towards polite curious conversation, the range of topics themselves is wide open. I have yet to see a site-wide blanket ban on, for example, adblockers. It is a contentious topic in the industry, there are entrenched trillion dollar interests that would rather have adblockers dissapear, and yet we can have a hopefully polite and informative conversation about the relative merits of subtopics in this area.