The anti-balaka have outgrown their name. These militias in the Central African Republic, once united under a moniker meaning “anti-machete” in the local Sango language, are exacting their own vicious revenge upon the mainly Muslim rebels who overthrew the government last March and waged months of terror against the Christian population. They are now accused of atrocities far worse than what first prompted them to take up arms. An Amnesty International report on Feb. 12 said attacks on Muslims in January by anti-balaka militias, made up of Christians and animists, had amounted to “ethnic cleansing.” Fatou Bensouda, chief prosecutor at...