If by your question you mean getting over the inhibitions to hit, I think it can be trained or induced out of you. It doesn't take Manchurian Candidate conditioning either. Most people don't want to hit others, your boxing coach was right. You get over that by realizing you have a stronger regard to not get hit yourself first. Running away always works and is a good way to not have hit or get hit. But it does tend to make you hate yourself and is sometimes the wrong response when you have obligations either familial, friendly, or occupational to fulfill.
I was a big, strong, peaceful kid who The Old Man despaired of when it came to standing up for myself. It changed my junior year in high school when I decided that I was by-God going to make the varsity football team no matter what it took. We were doing tackling drills and I hit Jeff Frank, a friend since 6th grade, so hard when he was carrying the ball it cracked his retainer in spite the mouthpiece he was wearing. I didn't want to hurt him, but I have never looked back since I made that decision over the Summer. I made varsity and was honorable mention in all-conference two years running. Mainly on the strength of several blocked kicks that took a few punters out of the game and one out for an entire season. So in my case it was determination to achieve another objective.
Hitting people with the hands is different than that though. It is true naked aggression. I stand in front of the kids during punching drills and hold up my hand as a target to get them over this and to improve their focus. I could use a hand held punch pad but that's for weak woosies and it doesn't provide the kids with the real feed back of what it feels like to hit human flesh. Also a lot of what we teach involves other techniques than striking so self defense isn't always about getting over the disinhibition against striking.
As for knowing who is the 1%? You can't. But you can use deflection, blocking, and side step evasion when an adversary moves in on you. Then you have other options for follow-up, counters, takedowns, throws, chokes, locks, or strikes of your own.
So in my own case I trained it out of myself. But others may need a drill instructor or sensei or coach to do the same. Hope this answers the intent of your question.