Why did Khawarij turn against 'Ali?

Answer 1

During 'Ali's rule as the fourth caliph (656-661 C.E.), a struggle over leadership arose between him and the governor of Syria, Mu'awiya. They joined battle, and then to spare further Muslim bloodshed, they threw their dispute open to arbitration. 'Ali's acceptance of arbitration weakened his case and alienated many of his followers, including the Khawarij (Seceders). This was due to the Khawarij beliefs that a leader of the Muslim world should be without impurity and this weakness belied 'Ali's personal failures and impurities. In the year 661 C.E., 'Ali was murdered with a poisoned sabre by a Khariji zealot.