It would be censorship to _force_ a company to say something they didn't want to say. That is clearly taking away their rights to free speech.
Disallowing companies from banning users would be forcing those companies to carry content they disagree with, thereby removing their right to free speech.
If they want the protections the phone company gets, they need to act more like the phone company.
I can even prove it.
That's how it works. Right. Now.