Plot: Lee Cowan talks with high school students participating in an exchange program between red and blue states. Also: Rita Braver sits down with Rachel Maddow, whose latest book, "Prequel," examines the fascist movement in America before and during World War II; Kelefa Sanneh delves into a new memoir by Sly Stone, of Sly and the Family Stone; Faith Salie takes measure of the history of skirts; Seth Doane examines the bitter reality behind the world's chocolate industry; and Martha Teichner finds out how a reimagined Ringling Bros