“We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant.” So said the philosopher Karl Popper near the end of World War II. The recent events in the Netherlands—traditionally seen as Europe’s most open society—have exposed the difficulties of applying this paradox in 21st-century Europe, where competing forms of intolerance are feeding one another, to disastrous effect.

In some ways the murder of columnist and filmmaker Theo van Gogh was a very Dutch affair. Victim and assassin crossed paths by bicycle in Amsterdam, where the Dutch policy of gedogen (roughly translated as benign neglect, or looking down your nose while turning a blind eye) has allowed a relaxed, self-regulating street culture to flourish. Van Gogh used free speech as a vehicle for racism and the Dutch tradition of “killing taboos” to boost his own career. He routinely referred to Muslims as “goatfuckers”; he called Jews “fornicating yellow stars in a gas chamber”; and wrote that a Jewish woman historian who criticized him “gets wet dreams about being fucked by Dr. Mengele.” He was no outsider artist but a friend of politicians, court jester to a certain circle of the Dutch elite. Pim Fortuyn, the charismatic anti-immigrant leader assassinated two years ago by an animal-rights fanatic, wanted van Gogh on his party’s ticket. Deputy Prime Minister and Finance Minister Gerrit Zalm, now leading the call for a war on radical Islam, played a role in one of his films. Of course (it should go without saying), he didn’t deserve to die.

This poster boy for free expression found a collaborator in Ayaan Hirsi Ali, an ex-Muslim who came to the Netherlands 12 years ago as an asylum-seeker from Somalia, where she had suffered genital mutilation and faced forced marriage. Her well-researched, outspoken opposition to such practices in the Netherlands won her a place in Parliament—first for the Labor Party and then for Zalm’s free-market VVD party, which demands the deportation of thousands of refugees, some possibly to face the tortures she has fled. Submission, the film she made with van Gogh that so angered his assassin, illustrates the intimate testimony of abused Muslim women with soft-porn imagery. Some Dutch Muslim women beaten by their husbands reacted angrily when it was shown on television, saying it made a travesty of their suffering. Hirsi Ali has also received death threats; she has been in hiding since van Gogh’s murder.

The journey of van Gogh’s accused killer, Mohammed Bouyeri, is almost a mirror image of Hirsi Ali’s. Born in the Netherlands to a quiet, moderate Moroccan family, he went to an academic high school and worked as a youth counselor at a community center. After his mother’s early death he got into petty crime and was seduced by radical Islam at a local mosque; according to the Dutch police he fell in with young men who were under surveillance as suspected terrorists, possibly linked to the Casablanca bombers. The letter he pinned with his knife to van Gogh’s half-beheaded body mingled Islamic formulas with the hippest Dutch street slang. It is Bouyeri’s Dutchness that has so deeply disconcerted the security services: He is no foreign fighter but an Amsterdam homeboy.

The panicked politicians of the right have not quite taken this in: Their proposals to ban imams trained outside the Netherlands, strip people convicted of terrorism of their citizenship and deport 25,000 undocumented migrants all assume that militant Islam can be kept out by building higher walls. Meanwhile, there have been more than 20 attacks on mosques and Islamic schools—two were burned to the ground—and revenge attacks on churches.

As the Amsterdam anthropologist Thijl Sunier explains, gedogen is not at all the same as integration. The Dutch government’s belated attempts in the 1980s to support immigrant workers focused mainly on their material needs, leaving culture, religion, and social welfare to community organizations—a throwback to the old Dutch “pillar” system, which organized society along confessional lines. The positive side of the present situation is, he says, “a growing awareness that Muslims are here to stay.” But, he goes on, “the wing of the Liberal [i.e., conservative] Party now in power [in coalition with the Christian Democrats] has increasingly taken on the rhetoric of Fortuyn.”

Claiming to rescue the security agenda from the right, centrist politicians across Europe are exploiting people’s fears of terrorism and social breakdown. In Britain the Labour Party has just unveiled a shamefully calculated program of security measures in preparation for the next election. The left, on the other hand, has itself turned a blind eye to the brand of jihadi activism shaped 20 years ago in the mountains of Afghanistan and now becoming, through the Internet, a discourse of dissent for disaffected youth from Fez to Finsbury Park. Despite having to face growing Islamophobia, the great majority of Europe’s 10 to 20 million Muslims are way ahead on this—which is why so many turned out to protest in France when two French journalists were taken hostage in Iraq to demand the repeal of the law banning religious symbols in French schools.

In the run-up to the invasion of Iraq a new conversation opened up in Europe between Muslim organizations and the traditional groupings of the left—trade unionists, feminists, peace campaigners and environmentalists, antiglobalization activists, the remnants of the old left sects. The relationship is new and raw, and mistrust on both sides runs deep. Privately, many on the secular left suspect Muslims of bringing in a faith-based, culturally conservative agenda and perhaps of giving cover to fundamentalism; Muslims often feel too beleaguered to reveal the discussions inside their own communities. Salma Yaqoob, chair of the Stop the War Coalition in Birmingham, was at the heart of the debates in Britain’s antiwar movement, and says it has been a very positive experience. Elsewhere, though, it has been more difficult, “If we’re not engaged, people say, What’s going on inside this community? Why is it so closed? If we do get involved, people say, What kind of alliance is this? and accuse us of collaborating with the fundamentalists…. Many Muslims now feel that their place in Britain is at stake. They are so scared, they don’t even want to speak among themselves.”

Islam is part of Europe, historically as well as demographically. It is also the Other against which Europe has defined itself, at least since the Crusades. If the “Muslim problem” is not to become Europe’s new “Jewish question,” that thorny conversation has to be continued and expanded, openly and without censorship on either side.