“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. …

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.