It is one thing for individual employees to have political views and to express them on their own time when off the clock and out of uniform. Their rights as private citizens should be protected. It is another thing for them to express their political views on the clock using company facilities. That violates the social contract between employee and employer and is certainly grounds for dismissal. But far beyond that is the violation that occurs when a group of employees uses company property to urge their company to take a political stance. I think that goes against the explicit policies of every major corporation in the US. The workers have the right to organize in a union, but no general right to organize politically. Management would be smart to terminate half and warn the other half: this is a workplace. Do your politics on your own time.