give him a slap and tell him he's too old for an imaginary friend.
seriously tho, if he starts preaching quote epicurus "Is God willing to prevent evil, but not able? Then he is not omnipotent. Is he able, but not willing? Then he is malevolent. Is he both able and willing? Then whence cometh evil? Is he neither able nor willing? Then why call him God?"
if that doesnt work tell him to count the deaths in the bible and see how many are caused by god (2,391,421*) and how many caused by satan (10) and ask him why an all loving, all good god would kill over 2 million people and why absolut