Freedom of speech is supposed to be every American's inalienable right, but Barbara Kopple's documentary about the Dixie Chicks examines the cost of certain comments. In 2003, at the start of the popular country-music group's "Top of the World Tour" (in retrospect, the title is almost ridiculously ironic) and as America was about to invade Iraq, lead singer Natalie Maines spoke her mind to a London audience: "We're on the good side with y'all. We do not want this war or violence. We're ashamed that the president of the United States is from Texas." Little did she know that her offhand remark, made in a city teeming with protests against U.S. involvement in Iraq, woul...