“I do human rights the way I played basketball,” John Prendergast said. We were sitting in the outdoor restaurant of an unfinished hotel in Juba, a boomtown of mud and shanties beside the White Nile in southern Sudan. It’s a restaurant where the South’s liberation leaders tend to gather, and these days they are in a buoyant mood. They have traded their fatigues for dress shirts and suits. A half-century of civil war seems to be culminating in independence. If a referendum on Jan.