How should one handle a well-known Daa`iyah in a foreign country who advocates asking the Prophet for intercession?

Tell him that the Prophet, peace be upon him, must not be asked after his death for intercession or anything else. Dead people in general must not be asked for anything; "If you invoke (or call upon) them, they hear not your call; and if (in case) they were to hear, they could not grant it (your request) to you" [Fatir:14]. So the dead should not be asked for anything, whether they are the Prophet or anybody else.  And ask him to prove that the Prophet, peace be upon him, could be asked for intercession; what is the proof? The Messenger of Allah—peace be upon him—said, "When a man dies, his deeds come to an end," and that's generalized to messengers and others.