The reasoning is, there can't be life without both a father and a mother, and the Caedaren at least know for a fact that there were two factors related to life being born in the form it is today. To reflect this, the actual moment life as it is now truly emerged is called the Birthing Hour: from the darkness of the womb into the sunlight smile of a proud father.
The Caedaren, then, feel that everything living is connected and should at least be tolerated to some point. In the early times, when the Caedaren still didn't practice the religion, they were hardly respectful of life as a whole in the manner they were after the advent of the Common Law. With the invasion of their homeland by the migrating eastern anardes, they... changed into pragmatical creatures. As for the future, it seems as if there is a bit of domestic violence in the air with Father's increased anger. Stupidly or not, the Caedaren and their preachers are hardly worried. They believe the only way the world can end is extinction - and they've almost been there already.