Mike you need to distinguish between saying that God almost certainly DIDN'T do something and that God COULDN'T do something. One of the assumptions underlying it is probably the assumption that God is honest - they He wouldn't leave huge amounts of misleading evidence around to fool us.
Here's a simple example. If someone stands up in court and says that God told him to commit a murder we regard him as crazy. But you would not say that God was incapable of sending those messages - you would sya that God would not do so.