I'm suggesting it has the same rules as a public square, which is what Twitter is. No incitement to violence, no obscenity etc but otherwise free.

You should realize those restrictions you suggest are regulated and enforced by the government and are applied inconsistently all the fucking time. Just look at how various different demonstrations in the last 5 years have been treated, and how some of them have ended in violence.

I really don't think you, or Trump, understand the ramifications of what you're asking for. You have this ideal, naive view of what's allowed in "public squares" that doesn't seem to match what happens.

See: Trumps belief he was persecuted by other government agencies. Which he complains about on Twitter. Which would now be answering to a... government agency...

If Twitter were a physical space there would be regular violence that would have to be shut down. The role of the government is to break up the violence if it occurs.

Again, that's a very idealistic "role of the government" that assumes there will never be anyone who interprets what should and shouldn't be allowed differently from you, or in a way that harms you.

And then, once that happens, now you have no recourse - even if you build another platform, it ends up controlled by the same regulators.