Well considering I live in one of the "far left" states and have had all kinds of jobs it basically comes down to this
I keep my personal beliefs to myself and away from my work. When I'm at work I'm there to do a specific job. If I'm not doing my job properly, I know that I can be fired.
As an employee, you basically learn to be a customer punching bag. You will ALWAYS, ALWAYS have customers who bitch at you, are rude to you, swear at you, etc. The best thing to do is keep your loving mouth shut and either continue trying to assist them or direct them to your higher up boss.
The only time you should act differently is if you're being physically assaulted. Even if you went to your employer about a customer verbally harassing you or demeaning you, chances are they'll come out and speak to the customer themselves or call the police depending on the situation. They aren't going to lower your pay or fire you, that is the dumbest stuff.