Commenters directed me towards this Associated Press article:

CAMBRIDGE, Mass. (AP) - The white police sergeant criticized by President Barack Obama for arresting black scholar Henry Louis Gates Jr. in his Massachusetts home is a police academy expert on racial profiling.

Cambridge Sgt. James Crowley has taught a class on racial profiling for five years at the Lowell Police Academy after being hand-picked for the job by former police Commissioner Ronny Watson, who is black, said Academy Director Thomas Fleming.

"I have nothing but the highest respect for him as a police officer. He is very professional and he is a good role model for the young recruits in the police academy," Fleming told The Associated Press on Thursday.

The course, called "Racial Profiling," teaches about different cultures that officers could encounter in their community "and how you don't want to single people out because of their ethnic background or the culture they come from," Fleming said.

Obama has said the Cambridge officers "acted stupidly" in arresting Gates last week when they responded to his house after a woman reported a suspected break-in.

Crowley, 42, has maintained he did nothing wrong and has refused to apologize, as Gates has demanded.

So, the former police chief of Cambridge, home to Harvard and MIT, is black. The current mayor of Cambridge is black. The governor of Massachusetts, Deval Patrick (Obama's stablemate in the Axelrod dojo), is black. The Attorney General of the U.S. is black. And the President is black.

Obviously, Crowley is sensitive to racial issues. My guess would be that Gates's playing of the race card, which can be a career-killer in Cambridge, got the cop's dander up.

Let's keep in mind, however, that just about all cops became cops because they like being dominant over other people. If they just wanted to help people, they would have become firemen. As Joseph Wambaugh, the cop-novelist repeatedly says, everybody loves a fireman. In contrast, Wambaugh's cops have issues, lots and lots of issues: divorce, drinking, and mental health (these days, about twice as many cops die by their own hands as on the job).