Thing is I’m all for a company dumping an employee who engages in hate speech, for example, in their spare time. It’s at-will employment so anything goes technically.

The problem here is that the guy is targeting something totally inappropriate: the concept of personal time itself. He’s saying in thinly coded language that he expects people to be working all the time. He wants to own their spare time. There’s nothing to do about this except for his staff to dump him and his company and quit their jobs. It’s at-will employment so anything goes.