I think your analysis of this situation would have greater merit if the larger body of statistics showing that white men disproportionately get away with unjustifiably shooting white men, than vice versa. The law, the fundamental institutions of the U.S.A. are promoting white supremacy (because they were initially created by people we would consider white supremacists). That is the point that matters. It is the fact that the police showed up to the scene of the crime... saw a black kid dead and a "white" man with a gun... and immediately gave Zimmerman the benefit of the doubt. If the dead kid was white and the shooter was black... what would the police have done? What would the NRA have said? What would the jury have thought? You know the answers to those questions.