Interestingly enough I have 2 friends who are police officers, and they do NOT want to be called "sir" in any way, shape, or form. To them "sir" is something reserved for high ranking officials in the military. They prefer to be called, "Officer." Apparently they take it very seriously, too, and have corrected people who called them, "sir."
The whole "sir" thing bothers me because it brings back some old childhood memories. One of my best friends growing up had a very abusive father. Part of that abuse was to constantly beat the 2 boys down by having them call him, "sir." Never was it "Dad" or "Father" but it had to be "Sir." To this day it just bothers me when I hear someone say they want to be referred to as, "sir."