"Great, this will lead to half the comments discussing BLM in a questionable and highly politicized manner on hacker(!) news ; this will surely be productive ... /s"
Political and sociological stuff is sometimes here on HN (and technology often overlaps, so they might be relevant of course), but especially those topics that have little chance of inviting meaningful discussion are questionable and might get flagged.
I consider "flagging" part of how this site works, and a meaningful feature. Right to free speech is not the "right to be listened to or read by others." HN also isn't Facebook, or Instagram (size, societal influence, scope in topics which are discussed) and you can still read it, upvote it, and comment on it even though it's been flagged. So I don't think it's as bad as you make it out to be. Posts about the banning practices of Social Media (be it Facebook, Youtube, Twitter or other platforms) are regularly featured on HN.
The post links to a neutral news story by Newsweek, which is a very reputable source. So what could be problematic about that article?
I fear that Hacker News might have a bias which makes them censor posts, exactly like Facebook does in this specific case. I don't want this to be true, but I can't think of any other reasons.