Wonderful, so Twitter is now a tool for corporate propaganda, Google is providing Censorship-as-a-Service API, Facebook is removing links classified as "Fake News(tm)", Reddit is deleting whatever mods don't agree with etc. Seems like we are going full steam into a dystopian society. I think I should start reading Solzhenitsyn to prepare for what is coming...
Tweeter and all others you mentioned are private corporations. Their goal is to turn profit to their shareholders - NOTHING MORE. He who believes these companies exist as a way for the mass population to voice their opinion and as a way to exercise democracy should rethink what these companies are all about. Note: I do not necessarily agree with that they do, just pointing out what they are all about.
By all means, curate your own back yard however you want. But misleading your users as to the nature of that curation should be actionable somehow. Enforced echo chambers are fine and dandy, so long as they are disclosed as such.