Why is U.S. President Barack Obama praising Islam to high heavens and why did he visit a mosque that is known to be a hotbed of Islamic radicalism?

The questions popped up in U.S. media a day after Obama visited a mosque and spoke at the Islamic Society of Baltimore, Maryland on Wednesday.

Talk-radio host Rush Limbaugh, a conservative icon, expressed puzzlement on why Obama, who professes to be a Christian, appears mesmerised by the Islamic faith, WND reported.

Limbaugh said he also could not understand why Obama goes out of his way to castigate Christians while acting as Islam's self-appointed apologist.

"Barack Obama, he goes into this radical mosque in Baltimore yesterday, he talks about how Islam has always been part of the fabric of America, and I stopped. I said, 'Really?' I didn't know that," said Limbaugh. "I didn't know that Islam had always been such a major, major part of America."

Michael Savage, another well-respected talk-radio host, shared Limbaugh's scepticism.

"Why does he have to sell this so hard?" Savage asked his listeners. "Have you ever seen a president of the United States who had so many positive things to say about Islam?"

Wednesday's speech was Obama's first at a U.S. mosque since he was first elected president in 2008. The Baltimore mosque is known for its vehement anti-Israel rhetoric and ties to terrorist groups. Terrorism expert Steve Emerson of the Investigative Project on Terrorism told WND that Obama was informed of the mosque's links to radical Islam but agreed to visit and speak there nonetheless.

Limbaugh noted that Obama "talks about how awesome Islam is all the time ... He says it's the most peaceful, most giving religion out there, that the mosque call to prayer is one of the most beautiful sounds in the world. And, at the same time, he's out there, and look what he says about Christians. He says he is one. Look, he talks about them as bitter clingers and they hold onto their guns when they're nervous."

Rev. Franklin Graham was also highly critical of Obama's mosque visit, rejecting the president's claim that Islam is woven into the fabric of America's founding.

"The foundations of this nation have nothing to do with Islam, but everything to do with the Church of Jesus Christ," Graham wrote on Wednesday on his Facebook page.

Speaking at the Islamic Society of Baltimore, Maryland, Obama said "Muslim-Americans keep us safe," according to WND.

He also pointed out that "the very word Islam comes from 'Salam' – peace," and that the standard Islamic greeting is 'As-Salaam-Alaikum' – 'Peace be upon you.'"

Obama also praised Islam, saying it "is rooted in a commitment to compassion and mercy and justice and charity."