I second the suggestion to take what is called a "Discovery Flight" offered by most flight schools. The CFI will review how planes work, and then take him up for an intro flight. Your friend will be able to control the plane to the degree he's comfortable. Perhaps the most eye-opening and reassuring part will be for the CFI to cut all power to the engine. He needn't tell your friend ahead of time. He can just do that, and then tell your friend, "now we are flying as if we lost all engine power." When your friend sees how much the plane glides, he'll overcome what is likely his greatest fear, which is plummeting to earth out of control.

I suggest the CFI not perform any spin maneuvers.