Maybe he has stopping power confused with the mythical 'knockdown power.'
No pistol round has the power to knock a human off his feet, else Newton's law would dictate that the shooter would be knocked down, too.
On the other hand, many pistol rounds can stop an attack, if inserted into the proper location.
This is another one of those posts where everyone else is wrong and your right.
Got it, carry on.
I voted .40 because I own 3 S&W's in .40.