Okay, I have to sound a little curt. You have no clue about rescue/shelter dogs. Your opinion is based on what society thinks and it just simply isn't true. It drives me crazy that people think that it they get a shelter dog that its going to kill their child. That's ignorant.
It's extremely ignorant for you to think you know exactly what any given shelter dog is like. You don't have any idea what their history is like. Does the dog have a spot on it where it doesn't like to be touched? Did they discover that spot at the shelter? Am I going to find that spot? Is my son going to find that spot? What will the dog do when that spot is touched? What other things send the dog crazy? All these things we just do not know.