He will go down in history as the guy who called the victims of September 11 “little Eichmanns”—a reference to the notorious Nazi bureaucrat who helped ship hundreds of thousands of Jews to concentration camps. Ward Churchill’s comment, included in a long-forgotten essay dug up by an enterprising journalism student, stirred a national debate about the power of unpopular words—and the proper consequences for those who use them. But the saga of the tenured University of Colorado ethnic studies professor grew more complicated in 2006, after allegations surfaced that Churchill had plagiarized, falsified or misrepresented some of his other scholarly...