As a veterinarian, I am glad Ontario put restrictions on Pit Bulls. The problem is the breed is poorly defined. Crossbreeds, Staffordshire crosses etc. Mastif type dogs are related. Of course owners that are kind and firm will have better outcomes with their Bullies. Training and leadership are necessary for all breeds but especially the potentially aggressive breeds. Most human and inter dog attacks are by intact males. Not long ago most dogs were bred for a job. Herding, guarding, fighting, hunting etc. In the last century dogs became pets and became part of the family. The traits originally selected for are still within the breeds. Without training and discipline these traits can come to the fore. Bullies and mastifs have powerful bites and tend to hold on, resulting in terrible damage to the victim. When several dogs are together, especially if not neutered, their aggression is increased. Leaving kids, especially small ones, unattended with any dog involves risk. That risk is much highly with Pitt Bulls and several other breeds. Especially if not neutered.
My 2 cents.