Like the current board does? I'm pretty sure there are legal protections against actually doxing or otherwise intentionally harming folks.
It's very telling that the board has reacted as they have. They will fight him, even if it destroys the company and the value of the stock. THAT should be illegal. That board will show themselves to be willing to harm their investors for a political stance.
The lawsuits should be interesting. This might very well establish a baseline for defining free speech in social media. NO ONE, Left, Right, or Middle should be able to silence the voices of political opposition in the agora. There is NOTHING wrong with allowing dissenting voices. We already have laws that keep people from slandering or otherwise harming people with violent speech.