That's not excessive at all IMO. The motorbike started to back up , looking as though it would drive away or even ride towards the cop. The only thing is that the cop wasn't easily identifiable when he pulled up or got out of the car (unless he had flashers that I didn't see). The gun was never pointed at the driver and it was only pulled when the rider started to back up. He looked behind him at the cop car making me think that he maybe knew it was a cop?
Anyways, doesn't seem like a big deal to me and I'd be surprised if they get anywhere with the court case. One big meh.