STOPPING POWER = penetration and expansion adequate to shred vital organs and cause cessation of assault.
KILLING POWER = bullet wound that causes someone to bleed to death but does not prevent them from advancing.
(My own words on those definitions)
The FBI has done this and for the most part people accept the fact that modern ammunition that does not get you 12" minimum penetration, is designed to transfer all the bullet's energy into the target without leaving it, and is going to leave a good permanent wound cavity, and hopefully cause hydrostatic shock...will stop someone.
Can a 22WMR penetrate 12 inches, maybe, maybe not. Is it's mass and velocity enough to do the damage needed to stop somenone, probably not with any reliability.
If you want to shoot and kill someone or expect someone to fall down when you're shot like they do on TV, then sure, go with the 22wmr or 22lr or 32acp, or 380. Not saying those guns can't luck out and actually stop someone because you lucked out and got that perfect CNS shot...but how are your odds vs. using an appropriate caliber (9mm and up)?
That should be someone's choice to make when they decide to pack a 22. My mother carries a little Smith 22WMR revolver in her purse and I've given her that disclaimer and she knows it's "better than nothing" and not likely to have stopping power. It upsets me, but that's her choice.