I was trying to pose a problem for the claim that God cannot lie, indicating that there was an argument against it. I was asking whether there was some way to believe in divine moral perfection, believe that lying is sometimes morally justified for benevolent purposes, and at the same time hold that God cannot lie. The kinds of lies that I have in mind have fairly transparent beneficent purposes behind them, and the overall effect is of course has to be for the eternal benefit of human beings. The title of Kant's reply to Constant is "On the Supposed right to Lie for Beneficent Purposes."
So far I haven't seen any attempt to resolve the paradox. It may turn out that the claim that God cannot lie can be defended. But I wish people would at least take a shot at the argument I provided.
To contrast this with the Calvinism case, you have reprobations which don't seem to have a beneficent purpose. With most of the problem of evil, if I use the range of responses available to someone who believes in libertarian free will, I can get a picture of why God permits various types of evils. There's a dim outline there, even though I can't come anywhere near to seeing how the details work out in particular cases. There's plenty of noseeum, but there is a good deal that I think I can see, which makes my position more acceptable overall, given the positive reasons I have for believing in God.
With reprobations, I'm just blind as a bat. Explanations like "God chooses a world with damned people in it so that the blessed will realize that they are blessed by grace alone" just don't wash at all. So this looks like a serious disadvantage.
This disadvantage could be overcome by 1) strong reasons for belief in God, 2) a strong case for biblical inerrancy and 3) a strong case for a Calvinistic reading of the scriptural evidence, involving not only a) a defense of a Calvinistic reading of the "positive" Calvinist texts, and b) an good explanation for passages which are ordinarily taken to show a universal intent to save. I'm pretty pessimistic about the Calvinist establishing 3b, however.