@Latte31 -I agree with you. I think that dog behavior is related to how the animal is treated. The most aggressive dogs that I have ever seen are always chained up.
I think that this fosters aggressive dog behavior because it is an unnatural state for the dog to be in and he is fighting it with his aggression. If the same dog were loose inside of a house or even in the backyard the dog would not be so aggressive.
I think that dogs that are mistreated become conditioned to be aggressive because that is the only way that they can protect themselves which is really how you learn to understand aggressive behavior in dogs.