The body language he uses with the non-trained dogs is *completely* different, and much less threatening. This was no experiment, it's theater to reinforce what dog trainer Bob there tells all the naysayers. The only thing proven here is AAA Guard Dogs wants more business.
When I was maybe 7 we (breifly) had a Chesapeake Bay Retriever that wasn't trained, none the less it stalked and slaughtered small animals in the back yard and tackled and snapped at anyone who came to the door that wasn't in the family, including my similarly aged friends. Was the sweetest dog in the world to the family though