ANKARA – Americans are generally tolerant people, and don’t like judging a person as inherently dangerous or threatening because of his religious beliefs.

But events since September 11,2001, have tested the ideals of Americans of non-Muslim faiths (or no faith, for that matter). We have seen the worst of Islam in the terrorist attacks in Bali, Madrid, Moscow, Istanbul, Beslan, Jakarta, London, Amman – all committed by those claiming to act in Islam’s name. Beyond that, most Americans now know that there are no churches or synagogues in Saudi Arabia, a tribute to the theocratic intolerance in the kingdom encompassing Islam’s two holiest sites. Critics of Islam, like Theo Van Gogh or Pim Fortuyn, get murdered in the streets, while others have to live in hiding, like Irshad Manji and Ayaan Hirsi Ali.

American attitudes reached a tipping point in the early months of 2006. First we witnessed the appalling, horrifyingly violent reaction to the Danish cartoons in so many parts of the Muslim world. Then the U.S. public responded with an emotional backlash to those riots and embassy assaults: the angry, vehement and loud opposition response to the proposed Dubai Ports World deal – when so many ordinary Americans were willing to bluntly state, “I just don’t want Muslims running our ports.” A recent ABC/Washington Post poll found that nearly half of Americans – 46% – have a negative view of Islam, seven percentage points higher than after 9/11. One in three Americans said that they believe Islam encourages violence against non-Muslims.

And now, on the heels of the cartoon controversy and the port deal, comes perhaps the worst of it all: Afghanistan’s trial of Abdul Rahman, who grew up as a Muslim in Afghanistan, but converted about 15 years ago while working with a Christian-run refugee aid group in Pakistan.

If you wanted to write a tale designed to get Americans furious with the Muslim world as a whole and with the Afghani government in particular, you would be hard-pressed to come up with an outrage more effective than this.

No faith likes apostasy, but leaving the faith carries the death sentence in Islam, at least according to the strictest interpretation of the Koran. Thankfully, that draconian punishment for apostasy is forgotten or ignored by many Muslims. But it’s still an article of faith for far too many others.

We just saw in the cartoon controversy how the West’s value of freedom of expression may be fundamentally irreconcilable with Islam’s value that its blasphemy laws apply to everyone, everywhere, all the time, whether they’re Muslim or not. Now, we may see how the West’s value of freedom of religion may be fundamentally irreconcilable with Islam’s bloody-minded zero tolerance policy on converting to other faiths.

Message to Kabul: Execute Rahman, and Afghanistan’s name will be mud here in America. The United States put a lot of effort into toppling the Taliban and really want to see your people become a strong, secure, independent and prosperous nation. But our nation is steadfastly adherent to the principle of freedom of religion. Killing this man for his beliefs will turn you into an enemy in our eyes.

Surely, there will be those who argue that we in the secular, modern, West cannot expect all countries – least of all Afghanistan – to embrace religious pluralism and ignore their faith’s teaching that conversion is punishable by death. But if the United States does not stand for religious freedom in its policies, what does it stand for? A mere diplomatic objection to his potential sentence cannot be enough; our State Department and the Bush administration must make clear that Rahman’s execution will alter the U.S.-Afghani relationship dramatically.

Similarly, this is, like the ports deal, one of those issues simmering with increasing heat in the blogosphere and under much of the Washington’s media radar. The Bush administration ignores the growing outrage over Rahman’s ordeal at their peril. Much of the president’s base is already rethinking their views on Islam; if the Afghanis kill Rahman, many of America’s Christians will be ready to pull out of Afghanistan and end any further aid to a government that declares war on Christian converts. It is not unthinkable that some would prefer to bomb this new Afghani government as mercilessly as we bombed the Taliban.

To kill a man for following another faith must be a deal-breaker.

Mr. Geraghty, a contributing editor to National Review, is the author of a book on terrorism and voters that will be published in August 2006 by Simon and Schuster.