The cop was doing his job, and certainly does not deserve a law-suit to be taken out against him. Yes, he acted insensitively, but at the same time think of his emotions-if you pull somebody over that is speeding that quickly, acting like the guy was and is clearly agitated, then as a police officer you are going to expect the worst. It may well affect you!
I agree that he acted insensitively (and certainly harshly), but to call it disgusting or to propose a lawsuit is ridiculous. There was a lot of pressure on both men, and both men could have handled it better.
At the same time, if the state police department wish to look into the matter then that is their choice. They would be within their rights to punish the officer and, in doing so, would need to rethink their entire position on situations like this. As somebody above said, if they made it wrong to treat somebody taking their dog to the vets as the police officer had done, would it be wrong to treat somebody taking their hamster to the vets in a similar way? Would it only be wrong if they really loved their hamster?
The correct way to deal with this, in my opinion, is for the state department to point out to the officer where he went wrong, and to teach him to think before he speaks in the future. If this is something that needs to be incorporated in police training in the future, so be it.
However, the be all and end all of the matter is that the officer did the right thing, but in an insensitive and thoughtless way. He doesn't deserve punishment, merely retraining.