I know in one of Sue Sternberg's videos, they show several aggressive puppies who are under 3 months old. They were just born like that, it was not due to the owner. Sue Sternberg is a nationally respected behaviorist who specializes in aggression. If a puppy is born with aggression issues, you can't reverse it too easily. Most likely there's a screw loose somewhere and the problems will only worsen as the dog grows.
I agree. There are certainly young, aggressive puppies - just as there are young, aggressive children. Everything is not always the fault of the parent or dog owner. There are dogs born with "a screw loose somewhere" just like there are people born that way. Sad, but true, and in those extreme case, euthanasia is best.