As far as .22 ANYTHING not having the punch, well, that's not really accurate. An actual look at the data indicates that for handgun calibers, it takes on average 2 rounds to stop an attacker (around 2.2-2.5 for 9mm, .40 S&W, and .45 ACP, and 2.6-2.8 for .22LR) based on around 20 years of data from police departments across the country. That's a negligible difference. At the end of the day, the size of the hole is irrelevant. The main issue is shot placement. You shoot someone in the head or heart or other vital organ, it doesn't matter what caliber the bullet happens to be.
And there have been people who have taken 20+ shots with 9mm ammo (the most popular handgun caliber in the US) and kept coming. For that matter, the AR-15/M4/M16 use .22 caliber ammunition. Sure, a .22LR or its more powerful cousin, the .22 WMR don't have the velocity to reach out to hundreds of yards. But then, your average shooter can't even shoot accurately at a hundred yards with a pistol. At the 7-21 feet ranges more common in self-defense situations, the power behind the cartridge doesn't really matter. I think that video that Bladite put up a while ago about that new "exciting" 9mm hollow point ammo is quite telling, considering the damage could be simulated with 2 shots with .22 LR. The guy in the video seemed to think that indicative of non-exciting damage for the 9mm (still plenty powerful, but not revolutionary), but it's also evidence that a .22 LR is plenty good enough for defensive purposes (which is possibly why Mossad seems to think .22LR is plenty good enough for their fieldwork). In fact, the main issue with rimfire ammo for defending oneself isn't the "stopping power" of the round. It's the inherent lower reliability of the ammo relative to centerfire ammo.
IMO, the caliber debate is utterly stupid. Did you know, for instance, that .40 S&W, the most hated of the popular calibers, has a higher one-shot-stop percentage in the real world than the similar 10mm ammo that people seem to think is so much better (and marginally better than 9mm as well). Or that .45 ACP doesn't actually stop people with one shot? There are hundreds of documented cases in which an assailant has survived multiple shots with .45 ACP hollowpoint ammunition (and good stuff, like Speer Gold Dots). The truth is, even in the industry, people have utterly wrong ideas about calibers that are simply not borne out by the data. Shot placement, not size, is the be-all and the end-all.