I agree that the Shiva of the Shaiva tradition and Yahweh could not coexist because their natures are contradictory and yet they are both described as being supreme. By definition, there can only be one supreme God, but why could there not be multiple gods that are subordinate to the supreme God? One definition of god is a supernatural, immortal being with superior powers. Angels and demons fit this definition. Even if they are not worthy of worship it does not follow that they don’t exist. I am certainly not proposing that polytheism is true, I’m just saying that if supernatural immortals exist why not call them gods?