It appears that the Cylons want to breed with humans in order to get closer to their god. I have a theory behind the Cylons (the human looking ones). My theory is that when the Cylons left the colonies to find their own world, after the armistice between the Colonials and the Cylons, there may have been some twisted human scientist who felt sympathy towards the Cylon cause and left with them only to create Cylon/Human hybrids through cloning. This explains why there are so many copies of human-looking Cylons. If you recall the "Gun on Ice Planet Zero" episode from the original 1970's Galactica, there was Dr. Ravishol, a human scientist who created clones that were put to work for the Cylons. This "human" may just be the god that the Cylons worship and by breeding with humans, they (the Cylons and their offspring) become closer to being like their god. Now, what if this "human" god that the Cylons worship calls himself Iblis (again, remembering the "Count Iblis" character from the original BSG series was a fallen angel). This human "Iblis" could be so deranged that he thinks of himself as being one of the gods of Kobol and declares himslef as the supreme god of the Cylons.