This isn't the first GSD to do this. They rehomed a previous one due to biting. That leads me to believe that it's them, not the dogs. I too had a GSD from a pup and she was an awesome dog. We spent a lot of time with her and training. She never bit anyone, but did come close, because I was being threatened. Drunk dude was yelling at me. As he was being escorted away, he spotted my dog and reached to pet her. Mind you, she was standing up, hair on end, growling and showing her teeth. I told him to leave her alone and he ignored me. Just as she lunged at him, I was able to grab her collar and keep her from biting him. Of course the dumbass was all butthurt because he *almost* got bit!!! 
