LAST WEEK WE LEARNED of another "massive" terrorist plot against American targets, this time thwarted by German authorities, Osama bin Laden has just released another cryptic video threat against the United States, and, six years since the events of 9/11, still we ask: why do they hate us?

Critics of U.S. foreign policy can cite many reasons for Islamist rage. But they overlook a more fundamental problem: To al Qaeda and its sympathizers, nothing is more deserving of contempt than the idea of faith as a free and rational choice--a concept more integral to American identity than any other Western democracy.

When Osama bin Laden excoriates the United States as "the worst civilization witnessed by the history of mankind," he has more than America's foreign policy in mind. To violent theocrats, it is not merely the content of contested doctrines that is offensive--it is their very existence. The United States, historically a nation of religious dissenters, is especially odious for this very reason.

Indeed, to the theocrats America's religious diversity is not just staggering but maddening: a Tower of Babel that has turned its spiritual infidelity into an art form. Even Mohammad Khatami, the former Iranian president hailed as a moderate, complains bitterly that Americans "try to disguise their crimes" with seductive rhetoric--the language of freedom, human rights, and pluralism.

Thus, Islamic extremists decry the spiritual corruption of the American "Crusaders" and vow a holy war reminiscent of Saladin's siege of Jerusalem, circa 1187. It does not occur to them that no Western nation has more emphatically rejected Medieval Christendom, with its faith-based repression and hypocrisy, than the United States. By keeping government out of the sanctuary--and priestcraft out of government--the U.S. Constitution has helped protect the integrity of all faith traditions.

America's Founders warned repeatedly of the "superstition, bigotry and persecution" generated by state-sanctioned religion. But they were not secularists, nor were they cynical about religious belief. Rather, they viewed "soul liberty" as a natural right--and a spiritual obligation. "It is unalienable also," argued James Madison, "because what is here a right towards men, is a duty towards the Creator." Their great accomplishment was convincing establishment elites that religious pluralism could nurture political and economic prosperity, just as intolerance guaranteed decline.

Compare these religious ideals to those held by numerous Muslim states--including Egypt, Iran, Pakistan, Saudi Arabia, and Sudan--with deep wells of anti-Americanism. All sustain a political culture that regards non-Muslims with dark suspicion. All have enshrined some version of Shari'a law, which criminalizes or severely restricts speech, worship, and free association of religious minorities. All have spawned terrorist activity against the United States and her allies. And all struggle with massive economic disparities and civic unrest.

Some Islamic leaders are slowly awakening to the problem. A few years ago a group of Muslim intellectuals and scholars, in a remarkable series of U.N.-sponsored reports, explored the causes of economic backwardness and political turmoil in the Arab world. They identified "an acute deficit of freedom" as the core problem. They even argued that Islamic governments should "protect the right of people and groups not only to worship as they wish, in private; but also to promote their values publicly in civil society."