Rick, there is a difference between insanity and the supernatural. The man could have claimed it was God telling him to kill people through the dog, it still would not prove God really did it.
You're completely ignoring the point. Does man sit in judgment to determine what is and isn't real in scripture? You would then make the presumption that the supernatural is impossible, and we must then remove every perceivable supernatural occurrence within the bible (scripture and Jesus are opposite, giving them make the presumption Supernatural IS real, and necessary). This would include the resurrection of Jesus, the entire premise of the Christian faith. If Jesus was wrong in believing in the supernatural, then his teachings are all meaningless. This would also extend to the very existence of God.
(1) To remove the supernatural from scripture is to undermine the possibility of bodily resurrection,
(2) To remove the bodily resurrection, is to remove the Good News of the Gospel, and make Jesus and the Scriptures a Lie.
" 12But if it is preached that Christ has been raised from the dead, how can some of you say that there is no resurrection of the dead? 13If there is no resurrection of the dead, then not even Christ has been raised. 14And if Christ has not been raised, our preaching is useless and so is your faith. " (1 Cor 15:12-14)
Understandably, if you reject the existence of an all powerful Creator, you would reject the premise of supernatural occurrence (such as talking snakes and donkeys). Clearly they do not talk by their nature (such as your example). However, within the hands of a Supernatural God, and within the revelation of scripture, the possibility is there.
Again, this question asked by the individual was whether we should take the Genesis creation account as literal. Our answer: Scripture both OT and NT take it as literal as the person of Jesus, and as such, being Scripture is our standard (1 Tim 3:16), we should follow it's lead, and not make ourselves the Lords of relative interpretation.
If you deny supernatural, it is difficult even to take part in this discussion. The point is moot.