You know better than I, IWS, that the police officer can use use his individual discretion in cases like this. Crowley could have walked away, since the only source of Gate's outrage, was Crowley's presence.
Clearly, disturbing the peace laws must be on the books, otherwise a neighbor blaring loud rap music could make my life a living hell. I firmly believe though that few arrests are made when an officer is called on a disturbing the peace call. Now, if the peace disturber refuses the officers request to stop his actions he will be arrested. So why do I think Gates should not have been arrested when Crowley requested Gates to shut up and Gates refused to do so? Mainly, because when I watch Cops (sorry, that is the best I can do) if the peace disturbance is caused by arguments between two individuals what the officer almost always does is get the individuals to seperate, to get one or both to return to their homes or somewhere else where they are no longer in the proximity of each other. Seldom is an arrest made. Crowley could have seperated the two parties in this disagreement quite easily. All he had to do was say. "Have a nice day, you raving lunatic" and leave. Crowley, was, most likely, not legally wrong, under current laws; he was wrong under my personal moral code, that emphasizes individual liberty and the Constitution as envisioned by our founding fathers, not the Constitution that the oligarchs in black robes have given us. Jefferson summed it up best "The government that governs best, governs least."