The World Health Organization recently decided it was okay to spray mosquito-infested areas — with DDT, that is. It turns out that DDT, when properly used, isn’t harmful to humans.

The decades-long ban on DDT goes back, of course, to Rachel Carson’s 1962 book Silent Spring. Because of the influence of that one, poorly researched, but oh-so-fashionable book, tens of millions of people in the Third World lost their lives to malaria over a 30-year period. Talk about the dead hand of the past! Carson’s ideas maintained their grip on disease prevention policy long after their deadly consequences were obvious.

But the discredited ideas in Silent Spring are as nothing in their destructive potential compared to the doctrines of multiculturalism — doctrines which have become, in effect, the unofficial ideology of the West.

Long before jihadists began their campaign of suicide bombing, the multiculturalists had installed the cultural equivalent of suicide bombs in nearly every classroom in the United States, Canada and Europe. Only these were time bombs set to go off decades later. They are exploding all around us now.

While radical madrassas around the world schooled Muslim children in the policy of no (infidel) child left alive, the diversity educators took pains to teach their students that no Western value was worth defending.

What did we learn? We learned that the values of Western culture are evil: It values racism, sexism and imperialism. We learned that all other cultures are good: They exist in a state of original innocence, and their values are beyond criticism. We learned to “respect diversity”: The more primitive or perverse the diversity, the more respect it deserves.

These were not just ideas. The dogma was backed up with speech codes, behavior codes, sensitivity training, diversity workshops and severe penalties for those who didn’t mind their multicultural manners. College admissions, school success and job security all depended on learning the rules.

By the turn of the century, the concept of minority assimilation was all but dead. It was widely believed that there was nothing in the majority culture worth assimilating to. Thus, when multiculturalism met Muhammad and his more aggressive followers, it was at a huge disadvantage. Islamists, it turned out, didn’t want to live in a multicultural society, they wanted an Islamic society. Faced with this challenge, multiculturalists responded in the only way they knew — with more sensitivity and respect. In a predictable gesture, California schools required seventh-grade students to memorize from the Quran and pray to Allah as part of an Islamic awareness course.

Despite the ominous signs that something is very wrong with the whole scheme, multiculturalist educators seem determined to stay the course.

They continue to urge their students to greater cultural sensitivity when, in fact, our culture is already suicidally sensitive. Educators prattle endlessly about the importance of adaptability, but many of them seem incapable of adapting to, or even recognizing, a world that has changed radically.

They are so in thrall to the doctrines of diversity that they have managed to miss the main story of our time — the rapid ascent of radical Islam. And their students have missed it too. In retrospect, it looks as though our students would have been better served if they had spent less time studying the Battle of Wounded Knee and more time studying the Battle of Lepanto, less time worrying about diversity and more time worrying about dhimmitude.

Of course, they don’t know anything at all about dhimmitude, which means they will be ill-prepared for a world in which dhimmitude will be the likely fate for hundreds of millions, and diversity will be only a dim memory.

In Europe, where many women have taken to wearing head scarves to avoid attracting attention, the connection between diversity indoctrination and dhimmitude is becoming clear. A 1995 study of British universities revealed that they were breeding grounds for Islamic radicals, and this appears to be true of European universities, as well. Many terrorists apparently learned their hatred of the West while attending Western universities. If you insist on telling people your culture is contemptible and deserving of a bad fate, eventually they will take you at your word.

While Muslims were being confirmed in their belief in their own cultural superiority, non-Muslims were learning to feel guilty about imposing their beliefs and institutions. The bred-in-the-bone response to any social problem was to assume that your own culture was at fault.

For example, even after the London tube bombings, police and politicians remained locked in the multicultural mode. They assumed that Muslims were angry because of discrimination and intolerance. What was needed was more sensitivity, more tolerance, more accommodation. Police refused to use the term “Islamic terrorism,” and there was general agreement among authorities that the greater threat to Britain lay in “Islamophobia.”

Not to be outdone on the multicultural front, Scotland Yard offered to consult with Muslim community leaders before mounting anti-terrorist raids — a policy that is still in effect.

Here in the United States, we’ve also found it difficult to remove the multicultural blinders. A good case can be made that the failure to stop the 9/11 attacks was due in part to a reluctance on the part of the FBI to follow up leads on Arab suspects for fear of being accused of ethnic profiling.

For similar reasons, the Federal Aviation Administration didn’t follow up on suspicious behavior by young Arab men on board a Boston-to-Los Angeles flight on Aug. 1, 2001 — a flight that proved to be a rehearsal for Sept. 11. You would have thought after 9/11 all that would change. But Transportation Department bureaucrats like Norman Minetta were so steeped in cultural sensitivity that even a little rational profiling was rejected out of hand.

Just as an earlier multicultural myth had proclaimed that AIDS was an equal opportunity disease, we were now made to believe that terrorism was an equal opportunity vocation, as likely to be pursued by white-haired Baptist grannies as by young Middle Eastern males.

Sometimes it seems our sensitivity knows no bounds.

Just recently, WorldNetDaily reported that representatives of a Muslim group with known ties to terrorism were taken on a tour of security facilities at O’Hare International Airport and briefed on counter-terrorism measures. They were assured by the Homeland Security official that customs agents were required to take a course in “Muslim sensitivity training.”

“Even after 9/11,” wrote Mark Steyn, “we can’t revoke the central fiction of multiculturalism — that all cultures are equally nice and so we must be equally nice to them, even if they slaughter large numbers of us.”

The world is an increasingly dangerous place.

Radical Islamists proudly proclaim their intention to establish shari’a across the globe. Translations of Hitler’s Mein Kampf sell briskly not only in Tehran and Cairo but also in bookstalls in London and Paris. Terrorist states like Iran are forging links with communist nations such as China and North Korea, and with communist-leaning countries such as Venezuela.

It is not inconceivable that nuclear states such as France and England will someday be controlled by Islamic fundamentalists.

Yet very little of this seems to register with Westerners, so many of whom have been brought up to believe that there is no such thing as a destructive diversity or a toxic tolerance. Schooled in a Blue Lagoon version of history, the average American or European finds it hard to imagine that any non-Western culture won’t respond to more understanding and dialogue.

And so the diversity educators continue on their path, focusing on what they perceive to be the really big issues of the day: the concept of “whiteness,” separate restrooms for “transgendered” folk, the crime of referring to Asian-Americans as a “model minority” — things like that. It’s understandable that Johnny can’t read the writing on the wall. After studying American Indian spirituality four years in a row in grade school, and racism and sexism awareness for four years in high school, it’s a little difficult to see the big global picture.

It may turn out that Rachel Carson was right about one thing. This time, it looks as though there really is a silent spring descending on the world. Only it won’t be the songbirds that fall silent, but the voices of reason and freedom. Just don’t expect the multiculturalists to sound the alarm.

William Kilpatrick was for many years Professor of Education at Boston College. He is the author of Why Johnny Can’t Tell Right From Wrong.