It's been awhile but I've seen some of the responses by police to these kinds of charges that boiled things down to a couple of things. First, the claim was that people "of color" tend to react differently to their authority and when faced with contempt for it, the result is pretty much what happens in every other pissing contest (be it corporate, public sector, politics, or everyday life). If you're hauling ass and get pulled over, following Chris Rock's guidelines probably won't hurt the outcome if this is the case.

Second, the other major theme that came up was that the disparity of treatment was the result of different circumstances. I'm not privy to all of them but the ones that came up the most were that some groups tend to think having insurance and a valid driving license is optional. Cops apparently think differently and the outcome causes substantive differences in the outcome of an encounter.

As part of a civics class I took years ago, we were required to read several of the studies on this topic too; while outdated by current standards, the explanations for the numbers were always lacking by both "sides" of the issue. The NAACP/ACLU/LULAC types always claimed racism as the first, second, and last reason for the disparity while the police groups always claimed methodological issues. Perhaps both sides were wrong?!?