They can stand out of the way, while looking for a new job.
Seriously, would you feel the same if the clerk refused to hand out gun permits cause she felt a moral compulsion to resist "gun violence?"
Seriously? Yes, I would. Principle is more important than rules. If the job requires me to violate my principles I must stand for changing the rules, not quitting my job. Ultimately it is principle that must stand. When principles are in conflict a state of conflict exists. Better to have conflict than blind obedience to bad law.
Can you conceive of any scenario where you would stand up for your beliefs? what would it take for you personally to feel called upon to stand up?