If I want to buy a weapon, even for target practice, I need a license that is pretty hard to obtain. Why don’t we do the same with dog breeds that are known to maim children disproportionately to other types of dogs?

If you really are a great dog owner and your dog is really as friendly as you say, you wouldn’t mind having both of you tested once a year in order to prevent bad owners from spoiling the image of that breed.