Both sides forked up here.
It started with Hill asking, "Why are you pounding on my window all crazy?" or however it was he asked it. The cop wasn't pounding on his window "all crazy." He was tapping on it and giving a lawful order to put the window down.
At this point, the cop had a choice to say something along those lines. Instead, he chose to act like a child and be miffed that this man was questioning his authority to tap on said window.
From there, it became about this cop proving his manhood. At that point it didn't matter that the subject of the traffic stop was Tyreek Hill. In fact, that probably made it worse for Hill, because some part of this asshole cop's lizard brain likely thought he'd have a great story to tell about how he took down an NFL player and didn't give a fork who he was.
At that point, the cop's partners had no choice — they had to defend their guy and play along, not unlike a situation where an umpire makes a bad call but the rest of the crew has to sell it.
Hill has had enough run-ins with the law to know that righteous indignation is not an affirmative defense. This cop working in the shadow of a stadium should have enough life experience to know that an NFL player driving a McLaren or whatever isn't going to pull a forking gun on him on forking game day.
Cops should be held to a higher standard of behavior and should always err on the side of de-escalation. It's also incumbent on the cop to use some situational awareness and consider the totality of the situation. If you are a cop and you wake up knowing you're about to have a Not Today, Motherforker kind of day, that would be a good day to call in sick. Unfortunately, for too many cops "Not Today, Motherforker" is their default attitude, and that leads to situations like this.