News outlets are properly marking this week the half-century which has elapsed since the assassination of Dr. Martin Luther King Jr. 

A bullet fired in Memphis, Tennessee, on April 4, 1968, cut short the life and work of the civil rights leader. In an abstract way, however, the bullet missed its mark, for it turned Dr. King into a martyr. It also turned his life’s work into a cause that can never be diminished; many leaders’ legacies fade in the light of subsequent events, but Dr. King’s quest, interrupted as his message took root in all Americans’ minds, remains forever fresh.

Many parts of the nation erupted in flames in anguish, protest, and sadly, some good old-fashioned looting, at the news. (You may think America is divided today, but look at 1968: twin assassinations, King’s followed by Bobby Kennedy’s; the Chicago Democratic convention; civil rights and Vietnam War riots and protest in many cities. We have weathered much worse than the...