I agree that Gates had the right to refuse to show ID. That he did anyway is to his credit. I would have treated the matter differently and made a formal complaint. But nothing that Gates did warranted arrest. It's clear that the officer knew Gates was who he said he was. A complete waste of tax payer money.
Have you read the report?
Now, I could be wrong, but I believe if you refuse to show your id to the cops, they have the right to arrest you until they discover your identity. Plus, he had a call about a break in, if Gates refused to show his id, the cop had every right to arrest him until his identity could be determined, that's the cops job. Do you really think that if someone sees you break into your own home and calls the cops that you have the right to refuse to show id and you won't get arrested?
Gates keep YELLING at the cop. He was beligerant and he refused to back down. His conduct was disorderly and that's why he was arrested. Had he not been a Harvard prof with friends in high places, he'd most likely still be in jail.