The riots were as inexplicable as they were deadly. Outraged youths marched through the streets, armed with guns, machetes, and nail-laden boards. They destroyed houses of worship and businesses owned by religious minorities. At roadblocks, they demanded to know the religion of each passerby. Those who answered incorrectly were beaten to death, then decapitated, dismembered, and burned in the streets. The victims—more than 100—had nothing to do with what had supposedly sparked the outrage. They were just in the wrong place at the wrong time.

Muslims rioting over the publication of Muhammad caricatures? Sadly, no. These were Nigerian Christians rioting over the riots. Muslim riots over the cartoons earlier in the week had left about 50 Christians dead and several churches ruined in northern Nigeria, where Christians are a minority. So in the south, where Christians are safely in the majority, revenge attacks against local Muslims tripled the body count.

Such scandalous behavior is worth remembering when we're tempted to arrogance toward those "poor, uneducated, and easily led" Muslims supposedly rioting over a Danish newspaper's cartoons. Let us also remember an earlier time when Denmark and Europe were ablaze with riots over religious imagery. In the mid-1500s, Protestants were so enraged by "graven images" and the veneration of saints' relics that they destroyed churches and ran through the streets looking for priests to assault. Centuries earlier, Byzantine Christian battles over the depiction of prophets and saints had become so violent—with thousands exiled, tortured, or killed—that the period between 762 and 775 became known as the "decade of blood."

How far we have come. Now some Protestants are among ...