A mother is talking quietly, almost without emotion, a monotone. The microphone crackles but relays her words to the crowd gathered beneath the Western Wall in Jerusalem. “We are here but we cannot forget there are 240 people buried but alive under Gaza,” Rachel Goldberg says. “They include my son Hersh. He was at the rave party. He escaped to a bomb shelter. Hamas threw in grenades and shot. Most of the people he was with were killed but Hersh was alive.” Her voice rises slightly. She has told this story many times, though not here, at the most important...