I'd like to point out that the video makes it dubious as to whether the man was actually being pulled over.In most of the cases that make it here reasonable people could disagree over whether the suspect has done something to precipitate the incident. Even in this case it could be argued that you should not get out of your car and move about with something in your hand when pulled over by the police. I seem to recall being told when you are pulled over that you sit in your car and keep your hands visible because police consider pulling someone over an inherently dangerous situation.
I'm not saying this officers actions were justifiable, but if they weren't it's not a libertarian v. non-libertarian issue. It's an issue of facts and circumstances.
At the very least It's clear he didn't think he was being pulled over.
There is no indication the police officer's lights or siren were active, the man pulls into the dealer's lot and immediately exits with a piece of paper in his hand. He is surprised to see the officer blocking his exit from the vehicle but when the officer steps aside he heads immediately to the front door of the dealership until the officer engages him in dialogue.
I think he had no clue that he was suspected of anything up until the point the officer grabbed his arm and threw him down on the hood of the car.
He does say the cop came up behind him with his lights flashing. That's generally a sign you're being pulled over.