Repentance is more than just sorrow for the past; repentance is a change of mind and heart, a new life of denying self and serving the Savior as king in self's place.
Many humanists in the West are stirred by a sense of outrage at what professed Christians, past and present, have done; and this makes them see their humanism as a kind of crusade, with the killing of Christianity as its prime goal.