Spike Lee's latest movie "BlacKkKlansman" is based on a book by Ron Stallworth, an African-American detective who infiltrated the Ku Klux Klan. At the film's New York premiere, stars John David Washington (who plays Stallworth) and Topher Grace (who takes on the role of former KKK leader David Duke) talked about channeling their real-life counterparts onscreen. (July 31)