Today is the 42nd anniversary of the My Lai Massacre, certainly not a happy memory—in fact , the opposite of that—but one well worth stopping to ponder. On this day in 1968, during the Vietnam War, the massacre was carried out by United States troops. Under the direction of Lt. William L. Calley Jr., a unit of the army tortured, sexually abused, and massacred more than 500 residents of the village. When the incident became public knowledge in the following year, it spread outrage around the world and significantly increased U.S. opposition to involvement in...