As I stood in the humid, dank cell, I found myself hesitating a bit, peering down into the cavernous doorways of the male slave dungeon of Ghana’s Cape Coast Castle. It was April 2001, more than a decade before President Obama would visit there. The worn brick-lined corridors told eerie tales of thousands of African captives held in cramped spaces, sometimes for months, standing shoulder-to-shoulder in their own excrement. That excrement, after 200 years, had hardened and raised the floor …