When I watched Eric Holder, Mr. Obama's Attorney General, glibly skim over the issue of the steep increase in mass incarceration of black and brown Americans over the last three decades, as he was being interviewed by Douglas A. Blackmon on a PBS rebroadcast from the University of Virginia's Miller Center, it got me to thinking about the problem Mr. Blackmon (a white Mississippi Wall Street Journal Reporter, who authored the incredibly well-researched Pulitzer Prize winning book "Slavery by Another Name"), had spend most of his adult life trying to get his hands around. ... W...