Had the cop not pulled the kid over for a non-offense this discussion wouldn't even exist. Should the kid have attacked the cop? Hell, no! But that would not have happened if the cop didn't initiate contact by pulling the kid over.
I don't disagree, but once the officer pulled him over, it was entirely the kid's actions that made it go so badly from there. He could have driven away with a ticket, but decided to kick it up a notch instead.
If an officer doesn't have the authority to escalate his actions in dealing with an uncooperative driver, then what's the point of them ever pulling anyone over?