PHILIP PULLELLA and THOMAS ESCRITT POPE Francis has rejected German Cardinal Reinhard Marx's resignation as archbishop of Munich over the Church's sexual abuse crisis, saying he agreed that it was a worldwide "catastrophe" but that the prelate should stay on. Marx, one of Roman Catholicism's most influential liberal figures, offered to resign earlier this month, saying he had to share institutional responsibility for sexual abuse by clerics over past decades. In a letter to Marx written on Thursday and released by the Vatican, Francis said he understood the motivation behind Marx's offer to resign, but would not accept it. "That…