He doesn't have the proof,because I have the proof that Satan doesn't exist
So,according to Christianity,God is an omnipotent and omnipresent being,or in other words,God is everything,and Satan is a being opposite of God.So,if God is everything,and Satan is the opposite of God,then that has to mean Satan is nothing,or in other words,he doesn't exist
That,of course,makes the whole christian phobia of Satan and his deceptions even more hilarious that it already is