Yep, he's right. The only two surefire ways to make a person stop their aggression is to disconnect the brain from the body with a high spine hit or headshot, or cause enough damage that blood flow to the brain is reduced and they black out. The second mechanism, at best, results in as much as 15 seconds before the brain is starved of oxygen and they go down. 15 seconds is an eternity if they are firing at you! At worst, they may bleed out minutes/hours after you are dead.
Mental/emotional state, chemical alterations of body chemistry, and body differences can all affect "stopping power" of any round. "Bullet Sponge" tales have been around for decades, usually a suspect hopped up on drugs or alcohol who takes dozens of police bullets before he stops fighting. IIRC, the unofficial record is an outlaw biker in IL that took 30-something 9mms from the ISP along with several shotgun slugs before he finally bled out and quit firing at them. Some people get wounded anywhere, even superficially, and stop fighting instantly. Others are "walking dead men" who fight until they lose consciousness despite things like having their heart shredded with a chestfull of buckshot. Brain shots are not even a sure thing, I remember an idiot years ago was playing "William Tell" with his buddy and drilled him right between the two hemispheres of his brain. The news showed him being offloaded from the ambulance with the arrow sticking out of his forehead! He was talking and acting like he was fine, and made a full recovery.
"Anyone worth shooting is worth shooting several times!"