I'd expect that case to be thrown out of court. Not surprised it was dismissed.
It isn't against the law to be disorderly or uncooperative with the police. Belligerent behavior isn't enough to support an arrest. A criminal charge of disorderly conduct requires much more. The fact that the officer asked to take the matter outside, thus taking it to an arguably public place, is absurd.
If the report is accurate: Gates acted like an idiot. I don't feel sorry for him. But that ain't a crime.
How it appears to me: Gates acted like an asshole, the cop overreacted in arresting him, and race had nothing to do with it (except for Gates's assumptions).