I don’t know if you were addressing the specific case mentioned, but if someone has a softball game they want to go to, and they say they have a medical procedure to take care of, that could easily be grounds for termination.
Best answer I can think of is to unionize and negotiate a CA that includes shift trade rights. Short term, I don’t think there’s much you can do if the company wants to be a dick.
Points for creative thinking, but I would prefer not to get fired and have to seek redress through the courts.