Taxi drivers provide a perverse service to the racial conversation when they refuse to pick up black people. Clearly it would be better if they stopped, so that we wouldn’t be left hailing the night air like fools or relying on white friends to sneak one past the censor like supplicants.

But if anyone is going to experience racial hardship, let it be the cab riders. For if you can afford to take a cab, then it is probably not a bad thing to be reminded that racism brooks no exceptions–up to and including the ability to pay. Racism discriminates against people on the grounds of race. Just like it says on the packet. It can be as arbitrary in its choice of victim as it is systemic in its execution. And while it never works alone (but rather in cahoots with class, gender and a host of other rogue characters), it has political license to operate independently.

It’s a basic lesson at relatively low cost. And yet the arrest of Harvard professor Henry Louis Gates Jr. at his home in Cambridge, Massachusetts, suggests we are doomed to keep repeating the lesson. Barack Obama was right when he referred to the arrest as a “teachable moment,” but given the brouhaha that has followed, it seems that even a moment involving the nation’s most prominent black intellectual teaches us nothing.

This lesson should come in two parts.

First, all such tales attempt to stage racism as a crude morality play, with individuals as absolute victims and absolute villains, rather than as a system of oppression that works primarily through institutions. The victim must have no priors and no drugs. And unless the perpetrator is photographed with a billy club in hand and uses racial slurs that are recorded on tape, we are supposed to give him the benefit of the doubt.

For an individual, that is fair. For a system, it is farcical. While it may be intriguing to speculate about what two people may or may not have been thinking, feeling and intending at any given moment, the proof of racism is in the odds. Black people in America fall foul of not just the law of the land but the law of probabilities as well. They are more likely to be stopped, searched, arrested, convicted and executed. A ridiculous black man and a ridiculous white man do not stand the same chances when put before a man with a badge, gun or gavel. The figures bear this out, and at the end of the day, nooses and burning crosses shouldn’t be necessary to demonstrate racism’s reach.