What I've trained is irrelevant.Show me the dog you’ve trained.
According to United Schutzhund Club of America:
The German Shepherd Dog must be well-balanced (with strong nerves) in terms of character, self-assured, absolutely natural and (except for a stimulated situation) good-natured as well as attentive and willing to please. He must possess instinctive behaviour, resilience and self-assurance in order to be suitable as a companion, guard, protection, service and herding dog.
The United Schutzhund Clubs of America (USCA) is a German Shepherd Dog Breed Organization guided by the rules of the organization of origin of the German Shepherd Dog, the “Verein für Deutsche Schäferhunde (SV)” in Germany. USCA is a member of the “World Union of German Shepherd Dog Clubs” and...
You said you've never seen a good handler/trainer with a "bad" dog. IMO, that dog in the video does NOT meet the breed standard and therefore is a "bad" dog according to the standard.