Just a bit of perspective.

Yes, the police have difficult jobs. Yes, they need to make split-second life-or-death decisions. But the resulting death is RARELY that of the police officer. According to FBI reports, 27 cops were killed in the line of duty last year. (Right, 27 too many, but 27 is a really low number for men and women who are supposedly under threat from every black teenager in America.)
Statistics are a little harder to come by in the category of civilians killed by cops, but "Federal officials allow the nation’s more than 17,000 law enforcement agencies to self-report officer shootings." That figure... hovers around 400 'justifiable homicides' by law enforcement each year." (hint: they are always "justified.")
And just in you're convinced that militarizing the police is a good idea for their own safety, in a rundown of the 10 most dangerous jobs in America, it doesn't even make it onto the list.
Perhaps if we spent less time telling them how threatening the world is to them and that all the people they meet are potential adversaries out to get them, they'd be less inclined to pull a gun every time they see a black boy playing with a BB gun.