“The enemy of America is not our many Muslim friends,” President George W. Bush declared soon after the 9/11 attacks. Mr. Bush’s statement set the tone for the tumultuous decade to come, one in which the nation prosecuted a war on terrorism in two Muslim lands while taking great pains to protect the rights of Muslim Americans.

Yet if the author Nathan Lean is to be believed, Americans today are caught in the grip of an irrational fear of Islam and its adherents. In his short book on the subject, Mr. Lean, a journalist and editor at the website Aslan Media, identifies this condition using the vaguely medical sounding term “Islamophobia.” It is by now a familiar diagnosis, and an ever widening range of symptoms—from daring to criticize theocratic tyrannies in the Middle East to drawing cartoons of the Prophet Muhammad—are attributed to it.

In reality, Islamophobia is simply a pejorative neologism designed to warn people away from criticizing any aspect of Islam. Those who deploy it see no difference between Islamism—political Islam and its extremist offshoots—and the religion encompassing some 1.6 billion believers world-wide. Thanks to this feat of conflation, Islamophobia transforms religious doctrines and political ideologies into something akin to race; to be an “Islamophobe” is in some circles today tantamount to being a racist.

American Islamophobia, Mr. Lean claims, is fomented by a “small cabal of xenophobes.” “The Islamophobia Industry: How the Right Manufactures Fear of Muslims” is less a book than a series of vignettes about some of these antagonists, who are “bent on scaring the public about Islam.” His Islamophobic figures and institutions range from political leaders like Mr. Bush, Sen. John McCain and New York Mayor Rudy Giuliani, who, Mr. Lean says, have “harnessed Muslims and Islam to terrorism”; to the pro-Israel community, which is alleged to be animated by a “violent faith narrative” and funded by magnates who inject “eye-popping cash flows into the accounts of various fear campaigns”; to pretty much everyone who campaigned in 2010 against the construction of the so-called Ground Zero Mosque near the site of the 9/11 attacks in lower Manhattan.

Mr. Lean tars with the same brush the likes of the scholar Daniel Pipes and the Muslim activist, physician and U.S. Navy veteran Zuhdi Jasser. Mr. Pipes, the author writes, is “deeply entrenched in the business of selling fear.” He portrays Dr. Jasser as a puppetlike figure, “a ‘good Muslim,’ one that openly and forcefully denounced various tenets of his faith.”

These are crude and uncharitable caricatures of these men. Mr. Pipes was one of the first Western commentators to raise the alarm about the subterranean spread of extremist attitudes in both the Middle East and among some Muslim communities in the West. Dr. Jasser, a devout Muslim, is the founder of the American Islamic Forum for Democracy, an organization that advances the notion that “the purest practice of Islam is one in which Muslims have complete freedom to accept or reject any of the tenants or laws of the faith no different than we enjoy as Americans in this Constitutional republic.” Both men argue that the real contest is the serious war of ideas raging within Islam itself, between the forces of liberalism and pluralism and those of obscurantism.

To Mr. Lean, though, any such distinction is simply a false perception manufactured by Islamophobes. Thus the author fails to grapple with the fact that, unlike average Muslims, Islamist terror groups like al Qaeda, Hamas and Hezbollah do commit unspeakable acts of violence in the name of Islam—actions that surely help account for why many Americans (49%, according to a 2010 poll) hold an unfavorable view of Islam, even when they view favorably Muslims that they personally know.

Mr. Lean also can’t seem to tell the difference between Islamist organizations and ordinary Muslims. Consider his view of the Council on American Islamic Relations, a self-proclaimed civil-rights organization that wields outsize influence on questions of Muslim integration in the U.S. Mr. Lean barely mentions CAIR and, when he does, it is in invariably glowing terms. The author lauds “cooperation between the FBI and CAIR” that supposedly “led to the capture of five American Muslim men in Pakistan suspected of trying to join radical, anti-American forces.” But he neglects to mention that CAIR was named by federal prosecutors as an unindicted co-conspirator in the Holy Land Foundation terror-finance trial of 2007. The same group, according to an unclassified State Department cable, sought to raise $50 million for an Islamophobia campaign from Saudi Arabia and the United Arab Emirates.

Islamist states and groups have been at the forefront of promoting the concept of Islamophobia. As far back as 1999, the United Association for Studies and Research, a group founded by Hamas leader Mousa Abu Marzook, published a book that purported to expose “The Truth Behind the Anti-Muslim Campaign in America.” After 9/11, Muslim states mounted a campaign to characterize the fear of Muslim violence as blind hatred. In 2004, United Nations Secretary-General Kofi Annan assured the world that U.N. “special rapporteurs continue to monitor the exercise and infringements of this right [freedom of religion], and to recommend ways to combat Islamophobia.”

According to anti-Islamophobia crusaders, though, even questioning the origins of the concept is itself a form of Islamophobia. Such dogmatism chills the crucial conversations that need to take place about Islamism here in the West. It also does a profound injustice to liberal Muslims around the world. After all, if Islam is dominated by its most violent and illiberal elements, and questioning these forces is deemed by intellectual elites to be a form of racism, then reform-minded Muslims really stand no chance.

Mr. Schanzer, a former terrorism-finance analyst at the U.S. Treasury Department, is vice president for research at the Foundation for Defense of Democracies.

A version of this article appeared January 10, 2013, on page A15 in the U.S. edition of The Wall Street Journal, with the headline: A Nasty Neologism.