The Dutch filmmaker Theo van Gogh, who directed a movie on the violence perpetrated by Muslim men against their women, was ambushed two years ago in broad daylight on a busy Amsterdam street by a knife-wielding jihadist.

In full view of passers-by, van Gogh was stabbed 28 times before his killer, reciting verses from the Koran, slashed the filmmaker’s throat in the manner Muslims slay sheep for sacrifice. The 26-year-old Dutch-Moroccan assassin was a first-generation immigrant who grew up in quintessentially Dutch liberal surroundings.

Hardly any Muslim groups, moderate or otherwise, voiced public disapproval of van Gogh’s murder except in the most formulaic way.

In Islam, “silence is a sign of acceptance,” as the Arabic Koranic saying goes.

In many ways, the savagery in Amsterdam showed how unbridgeable the gap is between Islam and other world civilizations — far more so, in my view, than the London, Madrid, Paris, and other bloody bombings by killers acting in the name of Islam, tragedies that took hundreds of innocent lives.

Along with multiple other attempts by European Muslims of Pakistani, Palestinian Arab, Egyptian, Moroccan, Algerian, and West Indian origin to kill and maim “infidels” over the past decade, the Amsterdam murder demonstrated the extent to which first-generation descendants of Muslims in Europe do not belong in any European society.

The question that hangs in the air so spectacularly now — particularly as England has been confronted once again by British Muslims plotting to kill hundreds — is this: What exactly are the Europeans waiting for before they round up all those Muslim warriors and their families and send them back to where they came from?

In the Netherlands, signs of the barbarity to come were posted loudly and visibly months before the murder. Spokesmen for militant and so-called moderate Islamic groups were calling for van Gogh to be chastised for daring to question the flawed Islamic practices toward women. Yet politically correct Dutch laws of free expression, the very same these Muslims killers and their enablers in the community flaunted, prevented the Dutch from stepping in.

A few days ago, the Saudi jihadist Muhamad al-Massari proudly told the New York Times that he has every right to run a Web site that calls for the violent death of British and American soldiers in Iraq. Around the time of the interview, Dr. Massari’s Arabic-language site praised a suicide bombing in Iraq that left 55 Shiite Muslims dead or injured.

By way of explanation, Dr. Massari — a physician who lives in London as one of many “approved” political refugees granted permanent residence in Britain — told the Times: “If you kill our civilians, we kill your civilians.”

Dr. Massari’s practices directly violate the British Antiterrorism Act of 2006, which was passed after the July 2005 transit bombings and makes it a crime to glorify or encourage political violence.

Last Sunday, speaking before 8,000 followers in Manchester, England, another Palestinian Arab Muslim and permanent British resident, Azam Tamimi, extolled the glories of martyrdom against the West. “Martyrs are those who stand up in defiance of George Bush and Tony Blair,” he said.

Despite its laws, England shares the dysfunctional political correctness of much of the European Union, which is preparing its own set of laws banning violent Islamic fascist mind-sets.

Yet Muslim fascists roam the landscape freely, speaking publicly, surfing the Internet, running fiery Web sites, extolling the murder of Westerners, and, most important, trampling on the Western democratic values of separation of church and state and freedom of expression — all in the name of Islam.

What is far more sinister is that these horsemen of the apocalypse benefit from near universal approval by Europe’s nearly 35 million immigrant Muslims.

A few, not nearly enough, European political leaders are beginning to see this situation for what it is: an irremediable clash of civilizations. .

The leader of the British Conservative Party, David Cameron, publicly broke the vow of silence on security matters in Parliament in mid-August when he chastised the Blair government for its glaring shortcomings on security and enforcement. “Why have so few, if any, preachers of hate been prosecuted or expelled, with those that have gone having done so voluntarily?” he asked.

Why, indeed.