He was the subject of a recent book, “The Enigma of Clarence Thomas,” which led to a flurry of articles and book reviews on his life and legal thought. A new biographical documentary, made by the conservative filmmaker Michael Pack, airs Monday on PBS. For the project, the justice spoke to filmmakers for 30 hours — an astounding feat for a jurist who once went 10 years without asking a question from the bench. “He would have never said, ‘Gee whiz, I should be an icon,’” said Helgi Walker, a lawyer at the firm Gibson Dunn who clerked for Justice...