[theorique]

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.