Schutzhund is NOT aggressive attack training. If you have ever trained at a club or owned a competitive SchH dog you would know the difference. Many clubs (not all) are filled with obedient dogs and dog savy responsible dog owners. SchH is a SPORT, not protection/attack training, that is a whole other ball game.
SchH has three main parts that equal weight is given to, protection is one of them (obedience and tracking are the others), however, a good SchH dog will have good nerve and be very confident and stable. Un-stable dogs do not make good SchH competitors. A fearful dog is NOT a good protector. A confident stable dog is. Character is very important. Listening to the handler is very important.
A part of SchH training before they can even compete for titles is a temperament test (BH) with all sorts of training around people with lots of obedience, this is both on lead and off lead.
Futhermore, SchH training takes place over many years. The protection is not started until the dog is much older as it is a sport, a process, and is very demanding on the dog and takes hours of training and dedication on the part of the handler. You cannot blame SchH for the behavior and temperament problems that might have been inherient in that dog and there is no telling what the first owner was like!
I really don't believe Schutzhund training is appropriate or called for in a family pet, and I'm not about to change my mind, after seeing too many "products" of that training end up in shelters and mostly euthanized. There may be some responsible clubs and owners, but IME, they're few and far between.