"If morality was absolute, such that it doesn't change with time, circumstances or belief, and part of the absolute morality is that we ought not take the life of innocent human beings--especially innocent children--then how do I justify God taking the lives of innocent children at the original Passover when the angel of death came through and killed the first born in every family?"
"How is it that God could allow the annihilation of thousands and thousands of people, whether that annihilation was through war or natural disaster? In fact, how is it that God could even command such a thing in the Old Testament if it is immoral to take the life of an innocent human being? How does it suddenly become moral because God Himself commands such a thing?"
In answering this question, we have to be careful of what is called Euthyphro's Dilemma and the dilemma is: Is morality something that is above God, that God must conform to, or is morality something that is merely the whim of God, such that God can choose to do anything He wants and it's still called moral? In the first case, it would mean that there is a law above God that He is subordinate to, which mean He would be less than God. In the second case, if morality is merely that which God says is right and wrong, then it seems that moral things are merely arbitrary and God could change His moral viewpoint at His whim, and this would then reduce His morality to His power. God has the power to enforce whatever He wants, therefore whatever He wants happens to be the moral thing at that time. Killing innocent children is immoral now, but tomorrow He might change His mind. And because He is God, after all, He can make that a moral thing, at least for Him. So there is the dilemma because it seems like you lose both ways.
God, being the Author of life, has the absolute right to take life away whenever He wants to. Simply put, He gives life, He takes it away. Life is His to do with what He wants. He can give it, as the Author, and as the Author, He can take it away again.
Life is God's possession so God may do with life as He pleases. There are certain things that are clearly God's prerogative. Can God create something and then destroy what He's created? Yes, He can do as He wishes, though His wishes are constrained by His character so He can't wish something that is immoral or inconsistent with His character. And there is nothing patently immoral about the Creator of life taking away life. It's immoral for us because when we take life, usually we are exercising a prerogative reserved for God alone.
There are a few circumstances where He delegates that power to us, specifically in my view, capital punishment. We know this intuitively, folks, because when men seek to make life and death decisions for others, what do we tell them? We say, "It's not right for you to 'play God.'" Well, of course, it's not right for man to play God, but it implies that it is right for God to play God.
Man and God have different prerogatives. It is inappropriate for men to take innocent life simply because we are robbing other human beings of a God-given gift and we are not to play God in that regard. But clearly God can play God. It is His role and He is not robbing when He takes away what He has given in the first place. It is something that is under His appropriate control. He can take a life anytime He wants. Taking innocent human life is wrong for us, because taking life is God's prerogative, not ours, which means it is appropriate for Him to do it, not us, and He can dispense and retract life whenever He pleases.
Part of the problem here is that we want to hold God to the same standard of morality He holds us to, as if the standard is above us both and man and God are on equal terms when it comes to behavior. Whatever we can't do, God shouldn't be allowed to do either. But every parent knows that such an arrangement is just plain false. Parents aren't constrained by the same standards that their children are constrained by, and in the same way God has a different set of prerogatives as well. Life and death is one of His, not one of ours, and that's why it is appropriate for Him to make His sovereign decisions with regards to the disposition of life and death. We are not to do so, and that's the long and short of it.