Are you aware of the term "public easement"? In many jurisdictions you are not able to block public access to your "private property" once the public gets accustomed to accessing that property. Same thing should apply here. You don't get to just open your private property for everyone to use and then close it for people you don't like politically many years later.
Twitter has already, on several occasions, been forced by the courts on "public square" grounds to take actions Twitter didn't want to for political reasons.
You're looking at the leaf on the tree and assuring everyone you see the forest.
Section 203 made them a public square because unlike the private property who would be liable for whats done on that land twitter gets a pass. And its looking more and more like they shouldn't. And if that happens twitter wont exist.