If I had to wear a uniform that makes me a moving target, I definitely would want to warn the "public" against acting on that temptation.
Or -- don't you believe in self defense?
Either way, though, it's quite arrogant. "Nobody (insults|attacks) me with impunity ... but I'll kick your ass any time I want and get away with it. I'll break down your door in the middle of the night, shoot your dog, shoot you, throw a grenade in your baby's crib ... and get away with it. And you aren't even the guy we were looking for."
Police in America are their own worst enemies. Their long history of high-handedness and misconduct make the racist left's lies plausible.
End of rant.
Have a nice day.