American police live in a place even more wondrous than the one you know from A Prairie Home Companion. In Lake Wobegon, all the children are above average. In Police Land, every cop is a model citizen, including those who outwardly resemble criminals.
When a cop thrashes or kills someone, the ensuing investigations almost always find that what the officer did was excusable, if not commendable. Steve Chapman notes, Jesus Christ would get tougher scrutiny from a band of angels than most cops do from the people who review their conduct.