He's free to whine about it, buy the company, or start his own platform. If he truly cared then he'd be lobbying for Congress to limit the "ban rights" of companies and individuals running platforms like Twitter (personally I would not vote for anyone supporting such a bill). Before the recent Supreme Court I would say that it would take an amendment; now I'm not so sure that such a bill would be overturned.

This is a little disingenuous. Twitter itself is the means of "speech." I don't think Musk or anyone else has stated that your Tweets should exempt you from consequences off the platform. Similarly, the ability for everyone to speak their mind on the world's modern town square doesn't give Twitter employees carte blanche within the corporate hierarchy.