You just outlined the solution yourself. If someone isn't doing enough productive work then fire them for that. Whether they were talking about politics or anime doesn't really matter.
But if he’s the only outspoken Trump supporter or trans-rights activist at the company you are going to spark a lot of rumors and ill will when you fire him. Whereas firing the biggest anime fan isn’t going to garner any notice.
I'm not sure what point you are trying to make. With these new policies in place it's more explicit that you are firing an employee for being a Trump supporter or trans-rights activist.
