Those of us here in California, by and large, don't really begrudge cops using an AR-15 for duty use. Especially given some of the circumstances and incidents they need to respond to. It's the idea that they can keep their un-neutered rifles after resigning or retiring from the agency that rankles most of us. Some central valley officer resigned to run his family's business and kept his two AR's. After a daytime break-in, police discovered his "assault rifles" and were ready to bag him until he showed he was the (then über privileged
) legal owner.
Consider this - in California, a Colt AR-15 (e.g. AR6721), owned by a police officer is now called a Patrol Rifle
 while the exact same rifle in the hands of a
citizen is an "assault weapon". Makes very little sense to those of us in the land of fruits and nuts.
¹ "Patrol rifle" is what VPC is now calling "assault rifles" when in the hands of police.