Berny, a few thoughts:
1) I agree with you that the Parler deplatforming and the banning of the NYP Hunter Biden were over that fuzzy line that nobody is quite sure exactly where it is. (Sort of reminds me of that old SCOTUS ruling on pornography --- it's hard to define, but we know it when we see it.)
2) I think it's important to distinguish between the censorship (yea, let's just use the word) of specific tweets/threads/articles, and the banning of entire people or companies from the platforms. When you ban influencers with large followings, whether that be Alex Jones or Candace Owens, it causes one to wonder if there's an ideological agenda afoot; if the platforms had focused on curating individual obnoxious posts rather than the entire account of the influencer, such concerns would be assuaged. (I’ll also add that when you ban an influencer who you are paying because it is profitable to do so, you invoke a lot of other regulations in business law, but that’s a topic for another day.)
3) The platforms, IMO, ask for trouble when they attempt to curate on standards which are subjective. An objective standard, such as "we remove any post which encourages or approves of the commission of a crime" is relatively easy to enforce, and in most cases the poster can cure a misunderstood post without incident.
However, when you attempt to curate standards which are less objective, the feelings and political leanings of the curator come into play, and the chances are high that deleted posts start to display a pattern of ideological preference.