Even more interesting, the more substantive question raised in the followup post -- what happens when we abnegate our moral intuitions? -- has gone almost completely ignored. I do want to eventually shift attention back to that, because I think it's an even stronger argument against Christianity (and religion in general) than the theodicy thing. But first I wanted to address a question raised by @Luke:
[A]re you predicating this argument on God having some sort of actual free will, but humans having no such thing?The question of free will lies at the heart of all moral issues because without free will there can be no moral agency. If a tree falls in the forest and hits someone in the head and kills them we do not count this as a moral transgression on the part of the tree. Why? Because the tree has no free will and hence no moral agency. Likewise, if someone is "mentally ill" (whatever that means) and they kill someone, or if a wild animal kills someone, we do not count those as moral failures because animals and mentally ill people do not have moral agency.
So we arrive at the age-old philosophical question: is free will (whatever that means) a pre-requisite for moral agency? Most people intuitively believe that it is, and this is the reason that many people intuitively recoil from Calvinist theology, despite the fact that it follows logically from premises that most Christians would say they accept. In particular, mans' free will is logically incompatible with God's omnipotence (or all-powerfulness, or whatever it is you want to call it). It is to the Calvinists credit that they recognize this and accept that man has no free will. Some of them (AFAICT) will even swallow the next bitter pill and concede that man has no moral agency, and that if this grates on your moral intuition, then your moral intuition is broken.
One thing you can't fault Calvinists for is being hypocrites.
But there is still this teensy-weensy little problem: if you abnegate your moral intuitions, then you no longer have any basis for distinguishing good and evil. Maybe suffering is good. Maybe Hitler was doing the work of God. Maybe "all-loving" doesn't mean what you think it means, and the Inquisitors really were doing what was best for their victims (or should we call them "clients"?) The fact that these suggestions make most people queasy can in no way be taken as evidence that they are wrong because, by assumption, your intuitions are broken. If I go on a killing spree, or rape children, who are you to say that I am wrong? In fact, I can't possibly be wrong because I have no free will, and hence no moral agency. Everything that happens simply happens as a consequence of God's will, because (quoting @wrf3) God is the only being with free will.
This is a logically consistent position. In fact, it is the only possible position that is logically consistent with any reasonable concept of God's omnipotence or all-powerfulness or whatever you want to call it. Man's will can either trump God's or it can't. And according to Calvinists, it can't. Because God created us, we are His playthings, to do with as He pleases. It would be fascinating to see just how far @wrf3's logical consistency will take him. He wrote:
Why a dinner thinks it can disagree with the one who cooked it seems to me proof that a part of our moral intuition is wrong.I wonder: if I were to kidnap Bob and cook him and eat him, would he object? What if I did that to his children, would he object then? On what possible grounds could he object, having abnegated his moral intuition? [Note to the NSA: No, I am not actually threatening to kidnap and eat Bob and his children. This is a thought experiment.]
If it is not self-evident to you that there is something horribly, horribly wrong here then there is nothing I can possibly say to convince you otherwise. You are a lost soul. I pity you (and I really pity your children!)
But if you are not willing to take the Calvinist plunge, if you harbor the tiniest bit of doubt that resigning yourself to the unspeakable horrors of moral abnegation might not be the right choice, then I have Good News: you do have free will (or at least the illusion of free will, and that turns out to be sufficient) and so you have moral agency. You can choose good over evil, truth over lies, peace over war, order over chaos, justice over injustice. It isn't easy. It takes work. It takes the willingness to accept responsibility, to be willing to make mistakes occasionally and learn from them, and to make your peace with the fact that you will fail to achieve perfection. In short, it requires growing up.
But it beats the hell out of the alternative. You can't make the world a better place if you reject the very idea that "better" actually means something.