There was a video on TV news a couple years ago where a shooter emptied his gun (a .22) into the head of the vic and he never even passed out. This was a lawyer, and most likely hard in the head, but was largely unhurt.
It takes a perfect shot with a .22 to stop someone who is intent on doing harm. A body shot may do it but it may give the attacker time enough to do you in before he goes down. And in a combat situation you will not have the time or the fine motor skills to make the perfect shot. It may come down to luck.
I love my .22 pistols, and have a few. I hunt with them, plink with them, and have lots of fun with them. I don't think they are enough to keep my family safe.