PARIS – Violent attacks on US diplomatic outposts across North Africa and the Middle East have once again raised the question of how to respond when Americans and other Westerners engage in provocative expression that others consider blasphemous. Though the attack on the US diplomatic mission in Benghazi, in which Ambassador J. Christopher Stevens and three members of his staff were murdered, may well have been planned, as the State Department has maintained, the killers clearly exploited the opportunity created by outrage at an anti-Muslim film produced in the US.