It is just a manner of fact that companies reserve their right to fire people to work for them with little to no excuse, and that is something we must live with, at least until there are changes of laws.
Yup, that's the life of being employed. We can be removed anytime the management wishes to. With politics or not, with something good or bad that an employee did, always think that they have the rights to do whatever they want to retain or remove an employee. But on this case, they all have the right to impose that rule because that's not right at all for an employee to do something inside working hours that's not in line with company's business.