In his 1952 book, Mere Christianity, Oxford scholar and theologian C. S. Lewis forcefully argued that you can not simply dismiss Jesus as a great teacher of morality without dealing with Jesus’ claims to be divine. 

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…or he would be the devil of hell. You must take your choice. Either this was, and is, the Son of God, or else a madman or something worse. You can shut Him up for a fool or you can fall at His feet and call Him Lord and God. But let us not come with any patronizing nonsense about His being a great human teacher. He has not left that open to us.

In the 1970s, Josh McDowell, a preacher with Campus Crusade For Christ, gave evangelizing sermons which summarized this reasoning as Jesus being: “Lunatic, Liar or Lord.” McDowell preached this alliterative challenge to millions in person and in print.

Believers have long sought to get people to examine what the gospels really say about Jesus and what they record Jesus as saying about Himself. Taking the gospel accounts seriously makes us seriously consider Jesus.

But recent presentations of this line of reasoning have needed to add a new element. Now the reasoning is “Liar, Lunatic, Legend or Lord.” “Legend” has been added to answer the arguments of unbelievers who do not accept the scriptural evidence that Jesus said and did such things. Skeptics cast doubt on the gospel record by a rough treatment of it that no other ancient records are subjected to. The trustworthiness of scripture used to be assumed, and then we could debate its meaning. Now many, even if they agree about what the text says, will argue that the record doesn’t mean much.

If people meant “legendary” to be “famous, remarkable and illustrious” then Jesus is more of it than any other. But skeptics use it to mean “fables, myths or stories” and dismiss Jesus' importance as presented in the gospels. 

C. S. Lewis was a great literary scholar, well trained in myths and fables, stories and legends. He was even a notable author of them. When he turned his scholarly expertise to the scriptures, he concluded: 

As a literary historian, I am perfectly convinced that whatever else the Gospels are they are not legends. I have read a great deal of legend and I am quite clear that they are not the same sort of thing…  (“What Are We to Make of Jesus Christ?” God in the Dock: Essays on Theology and Ethics, 1972)

As much as the skeptics like to say otherwise, it is not the search for truth, scholarship or reason driving them to reject Jesus. Rather, it is the usual suspects of selfish desire, pride and deception. The devil doesn’t care so much how or why you dismiss Jesus—only that you do.