> Private companies can't arrest you, put you on trial, sentence you to prison, or kill you

In many US jurisdictions they can do the first (and so can essentially everyone else.) They also do the last, often without legal consequences, though not as the outcome of a judicial process (but in civilized countries, government can't do that as the outcome of a judicial process, either.)

But they can use their opinion in such a way that I am not accepted by the majority of other companies in the sphere.

I'm not picking on you in particular, but this is a rather annoying argument that people bring up that is utterly nonsensical. Companies can and do cause harm to individuals. No they can't put you in jail but they can otherwise isolate you from society via making you unemployable, revealing personal information to social embarrass you, or barring you from essential services to function in modern society. To pretend they aren't is to be in denial to the scope and power and of modern companies. I say all this as an ardent capitalist for what it's worth.

Sure, but no one is claiming private companies can't hurt you. That's not what this is about. Note the specific term used: the government can kill you. It is the sole arbiter of what's legal in its domain. The first amendment doesn't exist to protect you from being shamed or embarassed for what you say. It exists to keep you from being jailed or murdered to censor the voice of the people.

So no, it's not "utterly nonsensical." Everything you're bringing up is completely orthogonal to the political theory of freedom of speech.

I mean that is exactly what the thread was about. Legalism, and the 1st amendment is very uninteresting as an argument about morals to me. The principle of the freedom of speech is an interesting moral argument which these platforms (publishers if we're being intellectually honest) are often guilty of abusing. Slavery was once "legal" yet when people talk about freedom the entire concept isn't hinged on the 13th amendment.