There are some names in the obituary columns that say more than the voices of the living. Such is the name of Dith Pran, who died in New Brunswick, N.J., March 30 at age 65. He was the Cambodian photographer who somehow survived the collection of killing fields that his country became after the Americans abandoned it. And who somehow made his way to the United States to tell the world about it. Millions of his countrymen lost their lives after the Khmer Rouge swept into Phnom Penh and began rounding up unreliable types — i.e., just about anyone who...