There have been a lot of diaries on the arrest of Henry Louis Gates, Jr., but I want to try to go a little meta here and discuss a larger point about how we understand the interactions between police and citizens--a point that I think is embedded in a prominent response to the Gates case.
The response I have in mind is the one that insists on second-guessing Gates: the one that often begins, yeah, the cop was wrong to arrest him, but why did Gates have to behave that way? Why didn't he just respond politely and let the cop leave? Maybe Gates was within his rights to yell at the cop, but by choosing to go that route he escalated the situation to its predictable conclusion. Everybody knows what happens when you talk to cops that way.
I doubt any of these commenters (except for a few obvious uber-trolls) are racist in motivation--they're not telling Gates that he, as a black man, was supposed to play Sambo to get out of this situation. They're in fact making a broader argument that's even more pernicious because it applies to all citizens, regardless of race or ethnicity.
The argument goes like this: when it comes to interactions between cops and citizens, there are 2 sets of rules. There are the written rules--the law--and then there are the unwritten rules--how everybody knows you're supposed to act towards cops. And while Gates was within his legal rights to play by the first set of rules, what he really ought to have done is play by the second set. By the first set of rules, you can loudly and rudely criticize the cop as long as you comply with his lawful commands; by the second set, you're supposed to reply civilly, withhold criticism, and remain cooperative even if you think the cop is harassing you or making requests that you're not, in the strictest legal sense, required to comply with. And why would you do that? Well, because you're innocent, after all, and because you just want to get this over with.
It's impossible to deny the existence of the "everybody knows" rules. The comments second-guessing Gates are evidence enough of that, especally when they're accompanied by broad, almost offhand assertions ("when a cop approaches you, everybody knows you're supposed to...") and by testimonials of personal success ("one time a cop pulled me over, and all I had to do was...").
What those commenters don't acknowledge are the costs of agreeing to play by that second set of rules. It's not unilateral disarmament, exactly, but it's a concession that expands the authority of cops and erodes the rights of citizens, and it creates a gray area of unwritten rules and a gross disproportion of power and remedies on the two sides. If a cop decides that a citizen has violated the unwritten rules, he's got a badge and a gun and can arrest the citizen--even if it's a bullshit charge that won't stand up--or do even worse. And we as fellow citizens are supposed to say (as so many have of Gates), "well, maybe it's not exactly right, but everybody knows that's what you get."
And what does the citizen get for agreeing to follow the unwritten rules? Well, you hope to get out of the whole thing more quickly and peaceably. And maybe you do. But what if you don't--what if you abide by the unwritten rules, and the cop doesn't? The answer is: you're screwed. The unwritten rules provide you no remedies--they're unwritten, remember, and unenforceable at law.
So in other words, you've surrendered your rights in return for no protections that you didn't already have; the cop, on the other hand, surrenders nothing and gets a great deal more latitude for action. And cops know that. They use that leverage to expand their latitude even further and to use the unwritten rules against you: if everybody knows how an innocent person is supposed to act, then what does that say about the person who acts otherwise?
Now, I'm not counseling you to yell at the next cop who stops you--you should obviously do what suits your temperament and your assessment of the situation. But before you invoke the rules that "everybody knows" against Gates or anyone else, remember that everybody needs to know the consequences of those rules, too.