Here's the police report. And here's an article from the Boston Globe detailing Gates's accusations of racism. Draw your own conclusions [
but note that we have a full statement from the cops, and we don't have Gates's side of the story. Here is Gates's version of events. FWIW, even if the cops' story is 100% accurate, I don't see what the point of arresting Gates was. Yelling at a cop isn't a crime, Gates clearly posed no threat to anyone, and the cop should have either used his training to defuse the situation or just walked away--he already knew that Gates wasn't a burglar, which was the original reason for the cops' presence.]
UPDATE: Personally, whenever I encounter cops in a potentially adversarial situation, e.g., during a traffic stop, I become absurdly obsequious, precisely because I know they have the power to arbitrarily arrest me if I piss them off. Law professor or not, the power dynamics in a confrontation with cops is not in your favor.