You claimed the vast majority of people you know are physically unable to kill. I think that is laughably naive.

If you mean that it is harder than you'd imagine to kill someone bareheaded, I also agree. But humans are tool makers and users. A big stick or rock to the back of the head was a common way to die in our distant past. And if you want to not allow any mechanical leverage in the killing, most people are _physically_ capable of pushing someone. That could be off a cliff, down the stairs, or on level ground where someone trips and hits their head.

This isn't a question of morality: it is a matter of physics.

I would say it is evidently true to me. As stated, humans are fragile. A punch or fall can easily cause brain injury leading to death. Get in an advantageous position on a person and they are going to have a real hard time preventing you strangling them unless they're trained/experienced in hand to hand fighting. On a purely physical level it is not hard to kill a person. This isn't even considering assistance from tools or infection, where a direct kill from fighting isn't required.

The number of people capable of this isn't 100%, sure, but it's closer to 100% than your posited 10 in 1000, 0.1%