I wasn't saying that any dog couldn't be vicious.
What I was saying is that people should be careful that they choose the right dog for their family. Given information like the story presented and information for the other side (which wasn't given) The chance for serious injury or death would be much greater with a dog such as the pit-bull than with a pekinese, not saying one could not be as vicious as the other but your chances of surviving a vicious dog attack from a pit-bull would be less because of strength and size.
And I have met a lot of small dogs whose behaviour is awful. Having a large dog myself, if my dog were to jump just once, even gently when we approached someone on a leash people would think its just awful, yet a small dog can jump and jump and jump near your ankles and peoples reaction is not the same. It seems worse cause they are large, so I understand your point that many small dogs are vicious/ ill mannered too.
I think a lot of the time people put up with things from small dogs they shouldn't, and couldn't handle were the dog much bigger.