Being in law enforcement I can tell you that there are bad people posing as police officers, people is people, catholic priest, president etc...
It is because of people like claude dallas and other scumbags who kill police officers that we are trained to be the authority figure and not MR. smiley. Different story if you're approaching someone you don't already know is a criminal, treat with respect and hopefully you get it in return. Was the dead officer a PR$%k? Maybe, but how many of you would pull a gun on an officer after he draws on you instead of putting your hands up and how many of you would make sure the officer is dead by putting a 22 through his head like a freakin possum? That final act is the clincher. There goes your self defense arguement in front of a REASONABLE jury. Next time I have to be a PR@#K maybe someone should put a bullet through my head?