Shooting at a gunman in an active shooter scenario is not barbaric, it's something you basically have to do.
Shooting at a gunman != shooting to kill. You're right that shooting at an active gunman can be a necessity. That doesn't translate to every police officer being an executioner. That argument is barbaric.
I'm not sure where you're going with this, but I'm assuming you think I meant that it's a deterrent that will stop 100% of people, which isn't what I said at all.
No, but using the word "deterrent" is meaningless if you have absolutely no standards. Will "shoot to kill" reduce schoolings by 1%? 50%? If all you have to use is the word "deterrent" to justify behavior, your argument degenerates into nothing. The same as capital punishment is "a deterrent". Just as life in prison is "a deterrent". If we actually look at crime rates in the US vs most other developed countries, it's really hard to justify any claim that the US has any real notion of what a deterrent is.
You then go off on a tangent about being monsters as an umbrella term and I'm just not gonna bother addressing it, as it's irrelevant.
Use whatever term you like. "Active shooter" works just as well. If I could trust that the police were infallible and brave or their mistakes were handled with all the same seriousness of an "active shooter", then I could possible support the notion of police aiming to kill active shooters. Instead, we see police/sheriffs who cower for shelter and men without guns who are shot and killed because they moved their hands towards their hips before they even moved towards being an "active shooter".
It's funny how the police are so afraid of ruining the life of a person who made a mistake in judgment because they reacted out of emotion in a tense situation but only if they're a police officer.