A person who tells people who are present about private and secret matters

One of the liars claims to know the Unseen. He recites Qur’aan over people who suffer from epilepsy and tells them to use papers on which he has written as incense, and he gives them amulets to wear. If a person who comes to him for treatment is a wine-drinker, he tells him that he drank wine the day before and that the rest of the wine is to be found in such and such a place, and says that he will not treat him for epilepsy until he gives up drinking wine. Then the person admits it. Please give us a fatwaa (ruling) on this matter. Is it permissible to sit and eat with this person and to greet him with salaam and pray behind him – as he sometimes leads the people in prayer? We have tried to advise him but he did not accept our advice, and says that he is doing the right thing. Please give us a fatwaa, may Allaah reward you.