It would be good to pass laws that make it illegal to fire someone over a twitter mob (or any kind of mob action). Anti-mob or anti-bullying laws. And/or initiate class-action lawsuits against twitter for encouraging this kind of behavior or failing to prevent it, resulting in significant damage to people's careers. It's far from being the first time this happens, so there's definitely a case to be made that twitter has known for a long time that this is a problem.
Edit: changed the choice of words.