What should be done with a man who infiltrated the terrorist group Hamas, spied for Israeli intelligence and broke up terror attacks, saving countless Israeli, as well as Palestinian, lives? Most people would say he should be honored. Not the U.S. government; it's trying to deport him.

Mosab Hassan Yousef was more than a spy. He is the son of a founding leader of Hamas, which made him among the highest prizes for Israeli intelligence. Yousef and his Shin Bet (Israel Security Agency) handler, Gonen Ben Itzhak, were in Washington last week, meeting with whoever would listen to them. Yousef told me — and Itzhak confirmed — that he never killed anyone and, in fact, prevented many from being killed, while providing useful information that thwarted numerous terror attacks.

In San Diego tomorrow (Wednesday) before an immigration judge, the government will charge that because of Yousef's "terrorist associations," he should be deported. Yousef tells me, "I acted like a terrorist in order to fool terrorists," but again emphasizes he never committed a terrorist act.

His is a remarkable story which he tells in a book "Son of Hamas: A Gripping Account of Terror, Betrayal, Political Intrigue, and Unthinkable Courage." Yousef is a man without a country. He was admitted to the United States in 2007 for medical treatment. His passport has expired. The government is holding his travel documents. If he is deported, he will be a prime target for those who consider him an infidel and traitor.

President Obama's "Muslim adviser," Dalia Mogahed, has endorsed a movement started by Turkey's Fethullah Gulen, which seeks to restore the Ottoman Empire and establish a universal caliphate; but Yousef, a Christian convert, faces expulsion from America. The administration has it backward.

In an interview, I asked Yousef what evidence the government intends to use against him. He says, "In my book, I give in great detail my affiliation with Hamas. I give an example that I gave five Hamas terrorists a safe house. This is right, but what they are missing from the picture is that I did this as part of Israeli intelligence." By providing them a safe house, Yousef helped Israeli intelligence identify and in many cases arrest terrorists, stopping attacks.

Yousef says he and Itzhak became such close friends that Itzhak, by testifying in his favor at the deportation hearing, will violate the wishes of Israeli intelligence, which worries about exposure.

Does Yousef have a message for Americans about the rapid construction of mosques throughout the country and radical Islam? First, he says, "you must realize that the word 'Islam' means submission. I am afraid of the ideas taught in mosques and the Islamic student movement in every American college and school in general. This ideology is a real danger ... it is an ideology of hate and revenge, of forcing people to convert to Islam or be killed. This is at the heart of the Islamic faith."

"But we need to understand there is a difference between Muslims and Islam," he says. "Muslims are wonderful people. They are peaceful, in general. I don't want people to be scared or look down at Muslims in this country."

Is this a distinction without a difference? No, he says, there are "cultural Muslims" who don't understand or read the Koran and then there are Islamists who take their faith and its application seriously, to the point of forced conversions, honor killings and terrorism. Yousef says there are no "moderate" Islamists and he suggests those Americans who think so are deluded.

Yousef dissects his former faith and its founder without pulling punches and his book is one Americans should read and believe. No wonder the government wants to expel him. He goes against what the Obama and Bush administrations and the pro-Arab State Department are trying to sell us.

A convert is often the best source of information about the dangers of his or her former faith. Yousef's deportation would be a victory for those who want to destroy America and everything it's supposed to stand for.

Cal Thomas is a syndicated columnist and author.