"It's not to excuse the behavior of the police.."
And yes, your comment is excusing the behavior of the police. Just saying that you didn't just excuse their behavior doesn't mean that you didn't just do exactly that.
"you're stupid if you expect to go to a really shady part of town and not get mugged. If you get mugged, technically, it's not your fault, but you should have seen it coming."
And that's what I think about this guy getting shot. It was less about the police being justified, and more about that person not thinking about the surroundings.
Edit: FWIW I do think the policeman was overzealous.
Unarmed people shot and killed by police last year: 48
It's a touch predicament, but I don't see a universal lack of prudence.
https://www.odmp.org/search/year/2016
https://www.washingtonpost.com/graphics/national/police-shoo...
This is one untypical case that makes the news, so you're thinking about optimizing decision making for this case; all the cases where police actually get shot don't.
In war, soliders are required to have an extremely high degree of certainty before opening fire. I think it's pretty safe to hold a higher standard to a police force that is dealing with primarily innocent civilians.
If they don't want to risk their lives, they can find another job. That may sound unfair, but it's more unfair to kill and murder someone who poses no threat.
That applies for business and software in addition to morals...