In my mind this is very similar to asking
Mr. Kinney to threaten a locked-and-loaded ED-209 with a gun [warning Robocop gore and raucous audio at linked URL]. ED-209 doesn't know it's a simulation and is not infallible. These kids were asked to play the role of potential bad guy, and one of the kids was given a substance that is generally associated with bad guys (by the police anyway). Sure the dog really just thinks the smell of the substance means the kid has his ball (if you know how drug dogs are trained) but the dog also knows that bad guys may try to hurt him, and he's in bad guy mode.
Bad plan all the way around. If I had an armed, autonomous weapon and directed it at some children, for a demonstration, and someone got hurt, I expect I'd get treated a lot differently.