Although I've been to this center, albeit many moons ago, I don't remember it being an issue then.
I agree, the sign is behind the white stop line which is to far away from the road. Even by stopping at the sign or line, the view is still blocked from the right. My question is what could a plausible solution be? By moving up the stop sign to the white line you'd be blocking the company's sign (and we know that ain't gonna happen) and you'd still have a blocked view from the right that could still possibly cause an accident with pedestrians/cyclist anyways. By adding another stop sign at the road, you'd be blocking the sidewalk while stopped at the second sign.
IMO, it's another example of how one law (in this case the sign ordinance within this city that requires all signs to be at ground level) creates unforeseen safety issues.
I also agree with you and the guy videoing, he does NOT have to present ID because he's not broken any laws...he's well within his rights!!