The thing that different people on this site have said about kinetic energy is that it's not a good measure of lethality. The reason being, the velocity term is squared so velocity is given more importance in the calculation than it should be given. So a light fast bullet looks like a more lethal round than a heavy slow bullet, at least on paper.
The easiest way to illustrate is by comparing the KE of a typical hunting arrow to a lightweight bullet like the 40 grain .22 bullet out of a .22 LR. Not many would choose the 40 grainer out of a .22 LR for large animals yet it has roughly twice the calculated kinetic energy of a typical hunting arrow that will pass clean through the rib cage of say, an elk. Now, some may say that an arrow kills differently than a bullet, but the same logic holds when you compare heavy slow bullets to light fast ones. The light fast ones win on paper with the KE calculation but not necessarily in the field on animals.
Like jwp pointed out, momentum seems a better way to go. If you calculate the momentum of the hunting arrow vs the 40 grain .22 round, the arrow wins.
The velocity term being squared gives it exactly the correct importance in the calculation of kinetic energy. The mistake is made in the misuse of the resulting number in a particular situation.
Misuse of momentum works the same way. If I toss you a bowling ball and you catch it you'll have more momentum to deal with than if I shoot you with a 22 LR. Yet which projectile would you rather catch?
