Given that Jack Dorsey just testified to Congress that he considers Twitter a digital public square, does the "it's a private company" work to defend them on such matters anymore?
Given the apparently coordinated action taken by Facebook, Twitter, Apple, and YouTube (Google), it doesn't seem to be independent, private companies acting independently.
It may not be a violation of the First Amendment, but it could be bumping up against antitrust law. Taken together, these companies have a significant near-monopoly in content distribution.
It's more like the power company or the gas company cutting you off because they don't like your politics. Yes, technically you can use a generator or get propane delivered, but the question is whether they should be legally allowed to cut you off.
If they are truly a public square and common carrier, then these platforms need to permit all content that does not violate the law.