Next time get his badge number and the car number and/or license plate. Document the incident – where, when, how, traffic conditions, etc. The more details, the better. Write down every word that was said if you have pen and paper (if not, use your cell phone to call your answering machine at home and dictate a message). Take pictures if you have a cell phone camera. Get a witness if anyhow possible.

Then check your state/local laws to verify that you have indeed the right to ride on the road. Chances are 99% that you can.

Then file an official complaint with the police department. Send a letter to each and every member of your city council, the mayor’s office, the chief of police, the local newspaper, your local bike advocacy organization, and whoever else you can possibly think of. CC everybody, so they know you are making a big fuss out of it - as you should.

That should be $10 worth of stamps but it'll hopefully teach that cop not to do it again. Of course they are above the law so there's no guarantee but it's worth a try.