Because they don't. Lucifer (the Devil, Satan, whathaveyou) is generally deemed a fallen angel, at one point God's most beloved. He coveted God's power and tried to seize it and so was cast down with the other rebellious elements. At no point is Lucifer/Satan ever viewed to be a God.
As for the Blood Cult. Yeah. Okay. "We hate daimons! Only -some- of us worship them! But we ally with them all the time and still seek to crucify others for doing the EXACT SAME THING! Even Sint! Ignore that they betrayed the daimons and cut them off from the old Netherworld with a Temple of Light while we marched along side the daimons to destroy bastions of humanity!"
Incorrect my dear man, The Fallen Archangel (not just a mere angel, some even suggest he was a Throne which I find doubtful) coveted God's Love of Humanity. Because God loved Humanity more than his Angels (Angels were placed under Humans).
He was jealous of Humanity.
