Writer-producer-director Stanley Nelson had trod the civil-rights path before for American Experience, and, as producer, emerged with thoughtful, informative yet undeniably and understandably emotional documentaries on, among others, Emmitt Till, Jesse Owens, and the 2011 study Freedom Riders, of which this new two-hour American Experience is a sociological sequel. It covers the 10-week period in 1964 in which student volunteers, carefully chosen and emotionally vetted, were sent to the toxicall