South African activist said a disciplined prayer life sustained him. Retired Anglican Archbishop Desmond Mpilo Tutu, the man who became synonymous with South Africa’s nonviolent struggle against apartheid, died Sunday at the age of 90. Tutu was diagnosed with prostate cancer almost two decades ago. The feisty spiritual leader of millions of Black and white South Africans seized every opportunity at home and abroad to rail against the racially oppressive regime that stifled his country for decades. His struggles earned him the Nobel Peace Prize and appointment to the leadership of a commission that sought to reveal the truth of…