When news came last Friday of a bombing in Oslo, Norway, followed by a shooting spree at a nearby youth camp, virtually everyone assumed this was the latest chapter in the bloody annals of Islamist terror. Hours later, the story took a dramatic turn: The perpetrator, Anders Behring Breivik, was a self-styled "crusader" against Islam and the enablers of "Islamicization." Has the Norwegian tragedy become a lesson in the danger of snap judgments -- and, perhaps, of anti-Muslim animus?

By happenstance, I found myself (indirectly) caught in the twists of this tale of terror. The day before the attacks, a prominent blog site, The Volokh Conspiracy, linked to the online version of my article on anti-Muslim bigotry from the August/September issue of Reason magazine. As news of the bombing trickled in, a few commenters scornful of any attempt to distinguish between Islam and radical Islamism weighed in with such gibes as, "Too bad about the timing of your essay. It would have been more persuasive on a day without a bombing in Norway."

Had the initial assumption been correct, it would have hardly discredited my article, which repeatedly stresses that extremism -- violent and non-violent -- is a major and serious problem within Islam today. Yet the actual events in Norway give a new relevance to the issue of anti-Muslim extremism.

Not that this horrific act mitigates the scourge of radical Islamic terrorism or its vastly greater proportions. Although Breivik's 1,500-page manifesto boasts that he is one of 80 "solo martyr cells" in Western Europe -- and counter-terrorism agents are taking the claim seriously enough to investigate -- there is no evidence so far that he was part of a terrorist network.

Nonetheless, last week's tragedy stands as a stark rebuttal to the dictum, popular in anti-Islam circles, that "not all Muslims are terrorists but all terrorists are Muslims." Some Muslim advocacy sites disingenuously downplay the Islamist nature of most modern terrorism, exaggerating the significance of mostly property-directed, rarely lethal acts by minor radical groups of various stripes. But the "terrorist = Muslim" meme on the other side has led to bizarre fantasies: that Oklahoma City bomber Timothy McVeigh was an al-Qaeda tool, or that Virginia Tech shooter Cho Seung-Hui was a secret convert to Islam.

There is now a contentious debate on whether the "anti-Jihadist" websites Breivik frequented, notably Atlas Shrugs and Jihad Watch, share some blame for this atrocity. Is there a danger in the mindset they promote? Ronald Radosh, a friend and a writer whose work I often admire, is harshly critical of such claims. In a Pajamas Media blogpost, Radosh deplores what he sees as an effort to smear authors brave enough to voice "uncomfortable truths" about the dangers posed by large populations of Muslim immigrants who reject Western laws and standards and support "jihad and sharia law."

Unfortunately, that is far too benign a description. The real message found on these and similar sites is that Islam is inherently so fanatical and evil that, unlike other religions whose sacred texts contain barbaric passages, it is impervious to reform or modernization; that terrorism is the only real face of Islam; that any moderate and peaceful Muslims are either liars or dupes who don't understand the nature of their faith; and that even liberal and secularized Muslims who have not explicitly renounced Islam are dangerous because they, or their children, could always revert to militant Islam.

In the "anti-Jihadist" blogosphere, valid critiques of Islamism coexist with a stream of false and misleading claims (that Islam permits believers to lie to infidels, or that all rapes in Norway in the last five years have been committed by Muslims). Modest religious accommodations for Muslims, such as foot baths for ritual ablutions in some bathrooms on college campuses -- hardly different from, say, kosher menus in student dining halls -- are seen as practically the first step toward mandatory burqas. Every violent crime by a Muslim is automatically blamed on his religion, and paranoid rumors of a Muslims connection are often flogged in cases where none exists (such as claims a few years ago that a University of Oklahoma student who killed himself with a homemade bomb was a Muslim convert and a would-be suicide terrorist).

To put it simply, these bloggers and activists traffic in hate: not toward Islamist terrorists or militants but toward Muslims in general. While they do not directly advocate violence, some of them, such as Pamela Geller of Atlas Shrugs, lionize Serbian war criminals as misunderstood defenders against the Muslim peril. All of this adds up to a toxic stew.

The "uncomfortable truth" is that the anti-Islam polemicists have some legitimate points. Yes, worryingly large numbers of Muslim immigrants, especially in Europe, resist acculturation and hold extremist views. Yes, large zones of Muslim culture today are dominated by radical fundamentalism and fanaticism that have no parallel in modern Christianity or Judaism except on the lunatic fringes. When a cleric like Yusuf al-Qaradawi, who spews anti-Jewish rhetoric and supports execution for apostates and homosexuals, can be regarded as an esteemed and "moderate" religious scholar, it says something about the state of the religion.

Yet many Muslims -- clerics, academics, journalists, activists -- are working for change. In today's world, the modernization of Islam is an urgent necessity.

"Anti-Jihadist" ideology denies the possibility of such change, instead agreeing with Islamic zealots that the West is at war with Islam and a liberalized Islam is impossible. What's more, Muslim-baiting discredits serious critiques of radical Islamism. To oppose this bigotry is not "political correctness" but common sense.