There are plenty of examples of animals running on after their heart being destroyed i am sure plenty on this forum have witnessed it. Give me a example of a person continuing on fighting after having their heart destroyed by a rifle bullet.
I don't think he was disagreeing with you. Purely theoretical here, but as long as there is oxygenated blood in the muscles and brain, someone could still act. The only sure "one shot stop" would be to sever the spinal column, since that would prevent the brain from giving instructions to the rest of the body.
I'm not saying there is a case of someone's heart being destroyed, and still fighting on, but from a theoretical standpoint, it's possible.
EDIT: To add to this, for those that say shoot through isn't an issue. According to Massad Ayoob in The Gun Digest Book of Concealed Carry, he concluded that in 1995 and 1996, 46% of bystanders who were shot by the NYPD (they didn't switch to HP until 1998) were due to shoot through (either through a person, or an object). Not saying this is conclusive, but shows that the possibility is there.
More on this, as to why HP ammo is going to be better in most cases, in the same book, Ayoob talks about the last high profile shooting before the NYPD switched to HP ammo. 4 officers engaged a man who they thought was pulling a gun. In 5 seconds, 41 rounds were fired. 19 rounds hit the man. 16 of the 19 hits passed right through. There's some interesting conclusions here.
First, of the 41 shots fired, only THREE ended up staying in their intended backstop. This left 38 rounds that could have potentially passed through the man and hit a bystander. Assuming HP's were used, and the same number of rounds were fired, it can be safely assumed that close to 19 of the 19 hits would have stayed in their intended backstop (and if they passed through, they would likely not have the energy to do any serious damage). This left 22 rounds that could have hit a bystander. Not a great number, but that's still about 42% fewer rounds that could have injured or killed someone.
The last assumption here, is it's VERY likely, this man wouldn't have needed 19 rounds to stop him if they were using HP. This means less lead flying through the air. Meaning there shouldn't have been 19 holes in this man. This meant fewer rounds fired, meaning fewer misses.
I know that I am making some assumptions here, but if you look at the history of police and personal defense use of HP vs Ball, you'll see that HP are safer for the person shooting them (quicker stops) and safer for innocent bystanders.
Now, would I want to be shot by either? No way. But I'm willing to pay a little extra to ensure that myself and my family are safe. I'll leave the ball ammo for the range.