After seeing the Chronicles of Narnia movie and hearing all the renewed interest in C. S. Lewis, I could not resist looking up my favorite quote from Mere Christianity. (For my young readers, when I was in college, we looked at Lewis, and Francis Shaeffer, with the same awe as you do John Piper).
Lewis stated the argument that Jesus' status as a great moral teacher cannot be divorced from his claims to divinity:
"I am trying here to prevent anyone saying the really foolish thing that people often say about him: I’m ready to accept Jesus as a great moral teacher, but I don’t accept his claim to be God. That is the one thing we must not say. A man who was merely a man and said the sort of things Jesus said would not be a great moral teacher. He would either be a lunatic — on the level with the man who says he is a poached egg — or else he would be the Devil of Hell. You must make your choice. Either this man was, and is, the Son of God, or else a madman or something worse. You can shut him up for a fool, you can spit at him and kill him as a demon and you can fall at his feet and call him Lord and God, but let us not come with any patronising about his being a great human teacher. He has not left that open to us. He did not intend to." C.S. Lewis, Mere Christianity