I understand that you were weaned on old Life Magazine photos of cops hosing Birmingham marchers and such, but come on.
Crowley's job was to confirm the place was not broken into, yes, but also to find out why a person was shouldering their own door; you never know, domestic situation, etc.
It's not significant that charges were dropped. It's a breach of the peace. A step up from a parking ticket. $50 fine. It's goal is to get an unruly person off the street (where the arrest took place). Go in the corner until you can play nice. That's it.
As well, it is not "telling" that he was arrested at his own home. Most people are arrested at their homes. What do you think, they get bank robbers in a shoot-out? If you're going to write about police practices, look into them. And imagine this, most people are arrested for BOP. So, the man who has built his career "fighting for equality" got the exact treatment a white man would have gotten he'd acted like an a-hole.
I can tell you, the last thing on Crowley's mind was busting Gates' balls. Cops, particularly in Cambridge, want to get out, grab a beer and get some overtime.
This may be really hard to accept, and contrary to all you picked up in your fantastic education, but some cops are really decent people. Some read and watch films and go to theater: they believe in social justice, are liberal and are willing to compromise their own safety to provided help (white, black, latino, whatever).
Sgt. Crowley has given EMT assistance to dozens of minorities. In the end, what have your pieces ever done?