Near the start of this year’s Sundance Film Festival, at a panel titled “Why Art Matters,” veteran television producer Norman Lear answered the question this way: “The arts start the conversation. When the world is saved — and it really does require saving — the door will be opened through the arts and then the politicians. Then the policies will follow.” And so the final day of the film festival saw the start of a national discussion about the Bush administration’s torture program. Robert Redford, Doug Liman, and other filmmakers and artists have united to remind Americans about prisoner abuse.