I was just going to let this comment go but I can’t refrain.....cabbies and grocery store workers, government or private sector employees? Cabbies and store workers represent their respective businesses. Police represent/work for ALL. You are comparing apples and oranges.
I see what you are getting at, and that is the way it used to be and should be—follow orders no matter the situation. It’s a complex issue that in the past was not as complex. Yes, they represent their businesses, but they also serve/assist customers of all different sorts of groups/backgrounds, etc. If Muslims are allowed to refuse or alter services in the private sector, they will CERTAINLY be allowed to refuse or alter service in the public sector.
For instance,
http://www.onislam.net/english/news/americas/469835-muslims-welcome-st-paul-police-hijab.html