There is no right answer here. These dogs can be great house pets or killers, however they act on instinct and training, as well as pack behavior. I wouldn't want to put a number on how many unpredictable dogs equal the life or even the scarring of my grandsons.
If I had my way the aggressive owners of these mutts would also be in cages, perhaps even cages containing other peoples aggressive dogs.
http://www.pitbullsontheweb.com/petbull/pete.php