Twitter, etc, right now has freedom of association and you'd like to take that away. At least be honest. And it's ludicrous to say that Twitter is the modern AT&T, which had a national monopoly on real-time person-to-person communication.
I can't take responsibility for "the left", but what I'd be doing is looking toward alternatives. Which I expect would work just fine for the left, which has always tended toward decentralization.
Even if we can't agree on whether monopolies should be allowed to censor [legal] public speech, we can probably agree that decentralization and federation (like some kind of social media blockchain) is the best solution.
...because there's no way any gov't can ever determine if some company is shadow-banning and manipulating feeds of the people they don't like, and if I can even get you to admit bigger government is almost always the worst solution to any problem then I've even made progress on that front as well.
Twitter is not a monopoly. You are the person advocating increased government intervention in social media, not me. And I definitely don't agree that adding blockchain snake oil is the best solution to any problem.
If you think BigTech companies (providing email, messaging, etc) should get to censor at their whim, I do wonder if you'd afford them the same level of discrimination if they were right-leaning rather than leftist.
I can't take responsibility for "the left", but what I'd be doing is looking toward alternatives. Which I expect would work just fine for the left, which has always tended toward decentralization.