Freedom of speech and freedom of association mean that Twitter has the right to put or not put whatever it wants on its website.

"Over 43% of the internet is consumed by Netflix, Google, Amazon, Facebook, Microsoft, and Apple"

Not only that but some of these companies collude to limit access both from competition and political opposition.

It seems that breaking up monopolies as in the past is not viable with tech empires like Twitter / FB, therefore some type of regulation in this area is where the focus needs to be, and I say this as someone who usually takes the libertarian position.

Facebook doesn't control whether you pick up the phone and call your friend to voice your opinion. Twitter can't prevent you from driving to your local bar and telling your drinking buddies what you think of the president. Then again, the bar owner can kick you out of his establishment if he disagrees with your thoughts and gets sick of listening to you.

Because again, your freedom of speech doesn't mean a business has to host you.

We are truly in uncharted waters at this point: historically, your newspaper comparison would have made sense, but it simply isn't applicable anymore.

At what point do we need to acknowledge that these platforms are the public square? When they control 99+% of online speech? When there is a worldwide quarantine meaning that people head to the internet to speak to each other, and meeting up isn't even an option? When being banned from one implies being banned from all of them?

Increasingly, there are difficult questions that we need to answer around this: Does this argument imply that even if all speech was transmitted through Facebook's servers, that wouldn't change the calculus around what "freedom of speech" means? How does this interface with laws worldwide? How does this interface with morals worldwide (the morality of the coastal US is not as universal as many people would like)? Is it morally acceptable for all businesses of a particular kind to collude wrt refusing to serve a particular person? Would it be morally acceptable for every business of every kind to collude wrt refusing to serve a particular person, whatever the reason?

Arguing from this place of finality by appealing to the way things currently work means that people get to ignore these questions. Not to mention that failing to look at changing circumstances is usually a bad idea: omnis conventio intelligitur rebus sic stantibus. This sort of argument generally reads a bit like rules lawyering to me: even if this is how the law works in letter today, it seems to be against the spirit of the law and broadly self-interested ('as long as the people getting banned are people I think deserve it, I'm all for letting the social media companies decide').

How about this example instead: Do phones have to serve you? Phone companies are user communication companies, after all. Seems like an appropriate analogy. Whereas a newpaper is more of a publishing company.

Yes, but there is the other side of that coin: a newspaper (as in the company) can get sued for libel or other such things, precisely because they have editorial control.

It's seems that social media companies would like to have their cake and eat it too. They are explicitly protected from their users content (thanks to section 230), and yet they seem to flex this immunity by arbitrarily blocking users, often without recourse. IIRC they have even occasionally flipped between being publisher or a platform depending on the question.

To be fair, there is no winning for large social media companies, either they preform this filtering and everyone hates on them, or they don't and everyone hates on them. I do not believe there is a perfect way to block only people who everyone agrees should be blocked, as every method has both false positives and false negatives.