Holding a gun doesn't make you immune to being injured or killed. Pointing a gun at someone doesn't always make them comply. A gun is a deadly weapon, but it's not a token of immunity and compliance. Shooting someone doesn't magically stop them or cause them to become a statue or a corpse.

> cops shoot people into the back

You're a police officer. You're called to investigate a violent rape by a suspect armed by a knife. The suspect runs and is quickly getting away. Do you:

1. Shoot them in the back

2. Let them escape and possibly rape someone else, hoping you catch them in the future

Neither of those is a good outcome and, just to make things more confusing, different states and departments have different rules in those situations.

> still victims are smeared

You can't know who the victim is until after the chips have landed. If someone gets shot by a police officer, they might have been an innocent person doing nothing wrong, or they might have been a violent predator who sexually assaults and murders kids for fun. When we're trying to assess that situation, you need all the evidence to come out - whether that hurts the cop (How many times have they used their weapons before? Do they have previous misconduct charges? Have they made racially charged statements previously?) or the person on the other side (Do they have a history of violence and crime? Are they a known felon? Were they on drugs?)

There are a few YouTube videos of use-of-force activists undergoing police training (https://www.youtube.com/watch?v=yfi3Ndh3n-g) and one of the things that stands out to me is that they are very, very fast to pull the trigger compared to most police officers. That isn't to say their points are invalid, but it's easy to criticize from a sofa and it's a different thing to be in that fight-or-flight life-or-death moment of decision making.