I don't believe it is a breed thing- I think any particular dog can be a danger especially to a child in some circumstances. A four year old daughter of a friend of ours was attacked by a Mastiff at a family picnic recently. They raise Mastiffs but the dog that attacked the child belonged to another family member. Thank goodness after surgery the little girl recovered.
We have always owned large dogs including Pits and Pit mixes and plenty of mixed breeds we weren't sure what they were. We safely raised children with them, but I never ever trusted any dog expecially a large one around children. Never. One of our girls was bitten on the cheek at a friend's house by their weenie dog and that was the only bad encounter our kids ever had with a dog.
I read that most dog attacks are on children and many by family pets- I have no idea why a pet would suddenly attack a child but I guess it might have something to do with nature driven predator/prey and possibly the dog not understanding that a child is a small person. Who knows really?
One reason I am against singling out any breed as being dangerous is that I am afraid if people blame "the breed" no matter what breed it is they may be careless with other dogs around children. That would be a big mistake in my opinion.
I guess the bottom line is that you should always watch and supervise any dog around children no matter what. They are usually at eye level with the dog and the animal may mistake them for another dog. This could cause the dog to pick a fight with what they believe is another animal.
You know, you are probably right in not singling out a particular dog. Just about any dog can snap. But a breed like a pit bull can cause more damage due to the fact that their jaws snap shut on their victims. This is probably why they have a really bad reputation.