Two years after the charges first surfaced, Kofi Annan has finally admitted that U.N. peacekeeping troops sexually abused war refugees in the Democratic Republic of Congo. "I am really shocked by these accusations," the United Nations Secretary-General told reporters last week. He shouldn't be. Allegations of sex crimes committed by U.N. staff and troops date back at least a decade and span operations on three continents, in places like Kosovo, Sierra Leone, Liberia and Cambodia. But rather than showing the kind of "zero tolerance" toward sexual crimes that Mr. Annan now promises, the U.N. has treated such instances with cavalier...