Aggressive dogs who attack

Yes, almost always incidents like this stem from dogs being improperly trained, or abused, or even taught to be aggressive on purpose.

I have to wonder though, if it is possible for a human to be born with a diseased mind, chemically imbalanced, and driven to act out evil, is the same possible for a dog? I'm talking about a defective mind incapable of being taught right from wrong.

I've heard people say "no dog is born bad", but I don't think we can say that for humans. If we did, every evil deed a human does would be excusable because they had to have been improperly raised or abused. Is it easier to blame humans for their actions, but not dogs, or is it actually medically impossible for a dog to be "born bad"?

I guess what I'm wondering is, can a dog be born with mental health issues that would make him irrational and unteachable, despite even the most seasoned professionals training?

Thoughts?