Cops are more likely to pull over and harass minorities, because minorities are [statistically] more likely to commit crimes. Minorities are statistically more likely to commit crimes, because they're statistically more likely to live below the poverty level and suffer from unemployment and lack of education. Minorities are statistically more likely to live below the poverty level because, historically, they've been denied equal opportunites in education and the workplace, and routinely suffer from the kind of discrimination that leads cops to pull them over for the color of their skin. And by assuming that these drivers are statistically more likely to be criminals based on their color [ rather than reason their way through the tiresome maze of social causes I just outlined ], these cops are just perpetuating a cycle of discrimination that breeds resentment and frustration in people who might otherwise feel a sense of moral obligation in a society that had invested a little more in their prosperity and well-being.
And although revealing the race of the cops doing the over-pulling might assuage some of that white man's guilt... all it really proves is that blacks and latinos are just as susceptible to racism as whites, and just as likely to discriminate against other blacks and latinos.