“In the real world, however, where a young, poor, black, or Latino man is far more likely to be arrested, incarcerated, and disenfranchised than a more affluent white man, where the fairness of many of the contemporary laws — in particular those relating to drug sentencing — that put people in prison is hotly contested, I would contend that disenfranchisement, even temporarily, overall does more societal harm than good. It is too heavily laden with the baggage of a culture divided along racial and class lines ever to be viewed as simply a criminal justice matter; its impact is too predictably absorbed by the economically marginal and the racially discriminated against to be viewed in isolation from broader social tensions.”