If the company disagrees with your politics

To an extent, yeah. If you're on Facebook or LinkedIn and posting holocaust denial or arguing that desegregation was a mistake, even if they are your sincerely held beliefs, a company would probably be safe firing you for bringing the company into disrepute with your posts. Unless it's something universally reviled or calls to violence, just posting "I voted for Candidate and you should too" would likely be considered an unjust termination if it just came down to your boss being a hardcore supporter of your preferred candidate's opponent. YMMV with this in the future, though. Of course, if your boss is not a total idiot, they could currently just fire you for your political views and dress it up with any reason, or even not give any cause at all, and most states would be fine with it since they have at will employment laws.