Five years ago, Ahmad Darrawi was one of the idealistic young Egyptians whose bravery stirred world-wide admiration. In 2011, he stood among the protest vanguard in Cairo’s Tahrir Square, and in the months afterward he often appeared on TV, outlining reforms for Egypt’s brutal and corrupt police. In the fall of 2011, he ran for parliament as an independent. His campaign ads showed a smiling, clean-shaven man in a gray suit under the slogan “Dignity and Security.” He was 32.

Three years later, Darrawi blew himself up on the...