I hate it when they say a certain breed is dangerous just because they've heard of a dog of that same breed attack somone. The worst part is that when you dig into the story, it usually wasn't even the dogs fault. It was either a child going up to a strange, tied up dog, or an abusive owner suffering a backlash of his treatment towards their pet. Even when I explain that it would only be natrual for the dog to react that way in that situation, they shake their head and say, "(insert breed here) are just really not to be trusted..."
Also, small dogs are nervous little things that are always afraid. That's why you'll always seem them barking and shaking.