> So there's some popularity point where after people use a platform to talk enough times, the platform is no longer allowed to moderate the speech on it? Why?
Yes, such a point exists. If you have a monopoly, for instance, then you should be subject to very different considerations. If you possess a monopoly on a discussion/communication platform so massive that it has become very important to societal communication and reach, then your ability to do what you want in terms of censoring content, should be curtailed in the favor of promoting free speech rather than the opposite. Meaning even if the monopolist wants to pursue their own political agenda and censor speech, they are barred from doing so. That is the price a corporation should pay for owning such an important platform, their responsibility should be greater, their freedom of action should be restricted more. You may be allowed to sell ads in that important quasi-public square, however you should not be allowed to restrict human rights in the square.
It is said, frequently and incorrectly, that only the government has the ability to censor. That's not correct. A monopoly, well positioned, can accomplish an identical outcome: it can restrict your voice in very comprehensive ways, including up to the point of literally denying you access to the Internet.
And a group of monopolies that conspire together in pursuit of a political agenda, well it's just that much worse.
Facebook (taking into account Facebook core + Instagram + WhatsApp) has a social media monopoly position, or something very close to it. They shouldn't get the same regulatory consideration as a modest sized political forum with 5,000 members.
YouTube has a monopoly in its consumer-upload streaming video segment. It's drastically larger than its comparable peers. Vimeo (who is #2 or #3 these days? I have no idea) should not get the same treatment as YouTube.
Google has a monopoly over search. It should not get the same treatment as DuckDuckGo.
Amazon (as with Walmart), should not get the same regulatory treatment as Joe's little corner grocer.
Twitter for its part, clearly doesn't have such a monopoly, even though it does have a massive, potent platform.
AT&T, Verizon, T-Mobile shouldn't be allowed to block your access to a phone account/number, and shouldn't be allowed to censor your calls. For exactly the same reason Facebook shouldn't be allowed to deplatform you.
I think it's very clear we're going that direction, there is no scenario where the biggest platforms escape being regulated in terms of their ability to censor and deplatform. If it has to be done at the state level to start, it will be.