Rev. Franklin Graham is leading a "disinformation campaign" against President Obama by attacking Obama's Christian faith and distorting Islam's theology, says a leading religion professor.

After CNN's John King gave Graham a full news cycle to raise a lifted eyebrow at President Obama's Christian profession of faith, Stephen Prothero, religion professor at Boston University, came on King's show Friday night to undercut Graham and question why CNN would ask an evangelist known to slur Islam, to speculate on its theology.

According to a transcript released by CNN, Prothero, author of

God is Not One: The Eight Rival Religions That Run the World, told King, the finding in a recent survey that 18% of Americans believe Obama is Muslim ...

... is because we have people who are supposed to be responsible public leaders, like Franklin Graham, who are spreading what seems to me like a sort of disinformation campaign... What Franklin Graham should say: 'Barack Obama says he's a Christian, he's a Christian, end of story.'

Prothero also pointed out that Obama prayed with Franklin and his father, America's most famous living evangelist, Rev. Billy Graham, in May but Franklin still repeatedly used the "if" word to answer King's questions Thursday on whether Obama has accepted Christ.

Prothero said:

Franklin Graham doesn't seem to be interested in focusing on preaching the gospel of -- of Jesus. He wants to be spreading misinformation about the religion of Islam. ... Why are we listening to Franklin Graham?

Prothero, who also wrote a book on Americans' ignorance about their own faith traditions as well as those of others (Religious Literacy: What Every American Needs to Know -- And Doesn't) told King,

.. it doesn't help the conversation we need to have as a public about Islam to be having people who are just basically spreading falsehoods about the tradition.

We should be listening to Muslims about their tradition. We should be listening to scholars about their tradition. But we shouldn't be listening to Evangelical preachers who are out to trash the Muslim religion in order to gain some political and perhaps religious advantage.

Prothero also pounced on Graham for cherry-picking quotes from the Quran that highlight violence. (In U.S. Protestant culture, picking quotes out of context from the Bible to prove a point is called "proof-texting."). Prothero highlighted

... shared beliefs and practices across Christianity and Islam. And we shouldn't be talking about the worst of the tradition of Islam and comparing it with the best of the tradition of Christianity.

When Jesus says, "I come not to bring peace, but a sword," is it fair to say, oh, Jesus is out to kill people?

No, because you read that in the context of the whole Bible. You read that in the context of the Christian tradition. That's how you need to understand passages in the Quran, is in the context of the whole Quran and in the context of the whole Islamic tradition.

Who are you listening to on Islam and Christianity?