Six years ago, on January 7th, 2015, two brothers armed with Kalashnikov rifles assaulted a building on Rue Nicolas-Appert in Paris, where they killed a maintenance man named Frédéric Boisseau and forced their way into the second-floor offices of the satirical magazine Charlie Hebdo. They asked for four cartoonists, by name, and executed each of them. They also killed four other journalists, a bodyguard assigned to protect one of the cartoonists in the event of just such an attack, police officer Ahmed Merabet, and a friend of one of the cartoonists. Following a nihilistic two-day crime spree, the brothers were killed in a hail of police bullets outside a printworks north-east of Paris. The ghastly murders at Charlie Hebdo shocked the world. Yet while the scale and violence of the incident were unprecedented, such attacks against cartoonists are hardly unknown. Throughout history, cartoonists have been jailed, kidnapped, tortured, exiled, and murdered. Ostensibly, the Charlie Hebdo cartoonists were killed for drawing pictures of the prophet Muhammad. (Two days after the murders, an al-Qaeda cell in Yemen …