Are you claiming that God says he couldn't have conceived of men engaged in this abomination, or that he didn't conceive of it?
Neither one of these interpretations is sustainable on a simple straightforward reading of the text.
Is it your assertion that God might have authorized this behavior if he had thought of it?
Rather, the statement God makes is plainly that this behavior is so diametrically contrary to the innate justice that characterizes his nature, and to what he had authorized for his worship that he never even weighed the possibility of authorizing or encouraging such behavior in any case whatsoever.
Open theists readily affirm God´s awareness of all knowable things past and present. Surely the open theist must admit that it is impossible for it to be the case that "it never entered God´s mind" that Israel would behave as she did. At the very least, according to open theists, God has known from all eternity that it could happen just as it did.
The passages in Jeremiah refer to the abhorrent practices of local idolatrous pagan communities around Israel. The specific behavior alluded to is the horrible act of Israel burning their children on the altars of pagan gods.
It cannot be denied that this is the behavior God is referring to through His prophet Jeremiah. However, we must note that God warned Israel against this exact sin hundreds of years earlier. Deuteronomy 12:31 warns Israel not to follow after the gods of other nations because "they even burn their sons and daughters in the fire to their gods." Later, in Deut. 18:10, God warns Israel that "There shall not be found among you anyone who makes his son or his daughter pass through the fire." In light of the reference to "Molech" in Jeremiah 32:35, Moses records in Leviticus 18:21 "You shall not give any of your offspring to offer them to Molech."
Now, can anyone rightly say that these statements in Isaiah accurately reflect an ignorance of God regarding the pagan practice of child sacrifice by fire?
Had God truly never considered this act? Clearly not, since He several times warns them against this very same act hundreds of years prior. These practices simply could not have entered God´s mind for the first time in Jeremiah.
Rather, we must understand that these phrases illustrate the godly hatred God has for this particular sin and the supreme displeasure God has in His children in participating in this sin. God is saying that this behavior is so vile, so wicked, so detestable that He does not want even to consider such a thing as happening, although, as we have seen, He in fact does know about such behavior.
AMR
God does nothing to interfere with man's free will. However there will be a judgment. Those who committ those kind of sins will be judged in the judgment and condemned to hell.
God has given man the freedom to sin. There is nothing to prevent us from going out tonight and killing someone, if we so desired. Just as we have been given a free will to sin, so we have been given a free will not to sin. The devil did not make Adam sin, he sinned by his own free will.
Man has the power to make choices. He can choose good or he can choose evil. I know of some people that are atheist and cultist that can outshine most Christians ten to one. No, they are not saved, yet they have the power to do good works.