By the time he wrapped up his speech with a rendition of Amazing Grace, one got the feeling that this was a modern-day, and perhaps more humorous version, of what Old Testament prophets regularly did to Kings of Israel: deliver brutally honest messages from Yahweh with little regard for their personal safety.

If the organizers of the national prayer breakfast ever want a sitting president to attend their event again, they need to expect that any leader in his right mind is going to ask — no, demand — that he be allowed to see a copy of the keynote address that is traditionally given immediately before the president’s.

That’s how devastating was the speech given by a little known historical biographer named Eric Metaxas, whose clever wit and punchy humor barely disguised a series of heat-seeking missiles that were sent, intentionally or not, in the commander-in-chief’s direction.

Although Obama began his address directly after Metaxas by saying, “I’m not going to be as funny as Eric but I’m grateful that he shared his message with us,” both his tone and speech itself were flat, and he looked as though he wished he could either crawl into a hole or have a different speech in front of him.

In fact, one could be forgiven for thinking that somehow Metaxas had been given an advance copy of Obama’s talk, then tailored his own to rebut the president’s.

Metaxas, a Yale grad and humor writer who once wrote for the children’s series Veggie Tales, began his speech with several jokes and stole the show early on when he noted that George W. Bush, often accused by his critics of being incurious, had read Metaxas’s weighty tome on the German theologian Bonhoeffer; he then proceeded to hand a copy to the president while intoning: “No pressure.”

Obama has been under pressure for some time now to somehow prove his Christian bonafides, for it’s no secret that millions of Americans doubt his Christian faith. A Pew Poll taken in 2010 found that only one third of Americans identified him as a Christian, and even among African-Americans, 46 percent said they were unsure of what religion he practiced.

Obama came to the prayer breakfast with a tidy speech that was clearly designed to lay those doubts to rest. He spoke of his daily habit of prayer and Bible reading, his regular conversations with preachers like T. D. Jakes and Joel Hunter, and even told a story of the time he prayed over Billy Graham.

But before the president could utter a word, it was Metaxas who delivered a devastating, albeit apparently unintentional critique of such God-talk, recounting his own religious upbringing which he described as culturally Christian yet simultaneously full of “phony religiosity.”

“I thought I was a Christian. I guess I was lost,” he matter-of-factly stated.

Standing no more than five feet from Obama whose binder had a speech chock full of quotes from the Good Book, Metaxas said of Jesus:

“When he was tempted in the desert, who was the one throwing Bible verses at him? Satan. That is a perfect picture of dead religion. Using the words of God to do the opposite of what God does. It’s grotesque when you think about it. It’s demonic.”

“Keep in mind that when someone says ‘I am a Christian’ it may mean absolutely nothing,” Metaxas added for good measure, in case anybody missed his point.

The eerie feeling that Metaxas was answering Obama on a speech he had yet to give continued, as he spoke about the uniqueness of Jesus Christ and the Christian religion.