I watched the video - he stopped, they came up to his truck and started slapping it. So he nudged them out of the way and drove off. It's not like he plowed into it at 60 MPH trying to kill someone.
What? They didn't come up to his truck, his truck came up to them. They were slapping it because he was "nudging" them out of the way. Slapping the hood to get his attention was a natural response to someone driving into them.
He was trying to drive through an intersection. They wouldn't move out of the street. Then they slapped his truck. It isn't like he was driving through a baseball field.