Maybe this is a choice between first amendment rights of the dominant platform companies vs. first amendment rights of 100s million of their users? If that's the case, wouldn't we want to take the users' side in this issue vs. platforms?
https://mtsu.edu/first-amendment/article/583/pruneyard-shopp...
> The California Supreme Court held the individuals had the right, under state law, to engage in the proposed activity. The ruling did not compel the shopping center to say anything at all, and the ruling did not prohibit the center from saying anything it wished, when and how it wished.
And it doesn't apply because:
> FAIR and PruneYard establish that compelling a person to allow a visitor access to the person’s property, for the purpose of speaking, is not a First Amendment violation, so long as the person is not compelled to speak, the person is not restricted from speaking, and the message of the visitor is not likely to be attributed to the person. The Florida statutes now at issue, unlike the state actions in FAIR and PruneYard, explicitly forbid social media platforms from appending their own statements to posts by some users. And the statutes compel the platforms to change their own speech in other respects, including, for example, by dictating how the platforms may arrange speech on their sites. This is a far greater burden on the platforms’ own speech than was involved in FAIR or PruneYard.
While I understand that people try to frame this as protecting First Amendment rights, this is actually very literally the government requiring the companies to publish certain kinds of speech. There is a provision in the law that would require any covered social media provider to carry all posts from any declared candidate. Turns out, though, there's a handy SCOTUS case that says that requiring a newspaper to publish replies from elected officials is unconstitutional abrogation of the newspaper's free speech.
Just as the First Amendment protects the freedom of speech, it also protects the freedom from compelled speech.
It only specifically constrains Congress. It does not mention state governments.
In addition, this falls under freedom of association; people (individually and in groups) are free to choose who they associate with, and include or exclude anyone they like based on any criteria they like (with certain specific exceptions regarding protected classes). "We reserve the right to refuse service to anyone" - for instance, a restaurant or store (or an individual at home) can kick out someone being disruptive, and so can a web host or social media platform.