In all my years here (5+) I can think of maybe one nut who said something like you seem to think is rampant.
Most of us have great respect for police officers and the work they do. It's a very difficult job and requires great dedication (and a great spouse)!
Where some of us tend to get critical is when we read of grossly inappropriate tactics. For example, breaking in an old lady's door, tossing in a flash-bang grenade, rushing in screaming four-letter-words while wearing ninja suits and face masks, and forcing the old lady to the floor.
It was later determined they were in the wrong house. She died of heart failure as a result of the Rambo-style raid.
I can think of very few times when such tactics are appropriate.
That said, real police officers are not involved in such stupid, rights-violating behavior, and deserve our wholehearted thanks and appreciation. Those who are do not deserve the title "police officer", and as such, are beyond the scope of the discussion.
Hostage rescue. An anthrax lab. And... what else?