Most people don't kill as a daily occurrence. It's possible to condition people to kill without hesitation. Why do you think ISIS starts conditioning their kids to be acclimated to violence and killing?
As I understand it from learning from people smarter than me, in groups, people will do literally ANYTHING to comply with what they perceive to be the expectations of the group. So they will go to the rally and enlist and put on a uniform and learn to drill with and shoot a weapon. Right up to the point of actually pointing that weapon and pulling the trigger they will be the biggest, baddest MFer in the Valley. At that moment, most will not kill, even with extensive training.
Watch the videos at Active Self Protection. The proportion of folks who walk around with a situational awareness of complete “head up ass” is astronomical. Then you have this small subset who take the effort to try to be aware, try to make a difference, and even then the proportion who can successfully draw on and put down a human predator is much, MUCH less than unity. Go to the website and watch. You can literally spend hours watching people who tried to make a difference die for their effort.
Really, we humans are fortunate violence is such a rare problem, when you think about it. I know I taught my children Situational Awareness until they were tired of hearing it. I carry. I would like to think I could make a difference. Thank God I have never been called to do so. I think the reason we have such a “PTSD” awareness is because these guys have trouble with dealing with killing. Now that they have become killers they have trouble dealing with it. Worse, that guilt is tied up with survivor guilt and blended in with a generous helping of being “shot at to no effect” which is said to have more kick than Crack. So the killing isn’t all of it but a good part of it, for sure.
I do believe you can train people to shoot without hesitation. I don’t think you can train a “normal, non sociopath” to kill without hesitation. I think the folks who have been training our shooters for generations know that and so we have the “combined arms” approach to combat we do. Find ‘em, pin them down, and kill them with mortars or artillery or even air support. No one has to come to grips with that “look him in the face” and kill him. I do believe the folks that train our warriors that DO have to do CQB, the SEALS, the Rangers, etc. understand this and that is why their training is so much more involved. It ain’t the learning to tie knots or field medical care or communications that takes so long. It is the “training to shoot with little hesitation” (one always needs SOME hesitation to avoid friendly fire if nothing else.)