You touched upon a whole lot of stuff here.
Yes, no political constituency - whether it be african-americans or another one - should be taken for granted.
Yes, the democratic party leadership, has been relatively lame at challenging the war, confronting voter suppression, and standing for economic and social justice.
Anyone who wants to vote Green or Libertarian is fine by me.
The criminal justice system in this country is a joke. The racial disparities are really a crime in and of itself.
Here's my take, however: you can't have social justice, without having economic justice first. The drug war, the criminal justice system, the failure of adequately funding urban and poor rural schools are all critical issues. But, without economic fairness and justice, those issues will never get any significant traction. Reactionaires understand this: keep people on the edge of desparation, keep them worried about losing their healthcare and pensions, keep them worried about their jobs getting outsourced, keep them worried about making it to the next paycheck, and they are going to pay little attention to the inequalities in the prisons or in the urban schools. Broadly speaking, of course.
Here's the deal, IMO: Economic empowerment leads to self empowerment. And to political empowerment. A political constituencie's weakest link in the chain, is the fear that comes with economic anxiety and despair. You address working americans (e.g., poor white americans, working hispanic and african americans) concerns about adequate health care, you protect their pensions, you pay them a living wage, you unlink the government from the stranglehold of multinational corporate interests and alleged "free" trade crap and outsourcing, and you free people up to be more concerned about social change. Do you think its a coincidence that some of the greatest social change came about in the 1950s 1960s when the nation was fat and happy; when labor unions were strong; when the public interest at least played a strong role in policy making? I don't think it was a coincidence.