Whilst I definitely agree that children are not safe with dogs 100% of the time, there are certain dogs and certain behaviours in dogs that are just a no-no. For eg: my dog is a border collie, lovely dog, very protective of my girls, especially DD1 (not really sure why he's more protective of her over DD2). My bil's dog is a kelpie. I wouldn't trust that dog as far as I could throw it. It's an inside dog, and very spoilt. They've recently had a baby and the dog isn't adjusting at all. Tries to push their baby out of the way all the time. Both dogs are very tempermental dogs.
You just can't be too sure. Not only with dogs, but most animals.