How dangerous is belief in conspiracy theories?

Dutch journalist Maarten Reijnders wrote a book about the currently most popular and (in)famous conspiracy theories and their proponents in the Netherlands. The book, titled Complotdenkers – Hoe gevaarlijk is het geloof in samenzweringstheorieën? (‘Conspiracists – How dangerous is belief in conspiracy theories?’) was deliberately published on 11 September 2016, because the 9/11 Truth movement is one of the most prominent of these phenomena in Western society at the moment. Skeptic Pepijn van Erp wrote a review; here is an excerpt:

Reijnders defines ‘conspiracists’ as people who believe in lots of different conspiracy theories at the same time, or draw rather far-reaching conclusions from such a conspiracy belief system. He calls a collective of such conspiracists a conspiracy church. That is a broad church, with many schisms. With liberals and literalists. With soft, kind and harmless believers, but also with some extremist fundamentalists. (…)

It can lead to contempt for innocent people and minorities, and we can still see enough suffering caused by that today. And we also know the example of the disastrous HIV/AIDS policy in South Africa under Mbeki, based on completely pseudoscientific ideas, that has led to an early death for an estimated 330,000 people.

Comedian mocks conspiracy theories

Dutch comedian Arjen Lubach is well-known for his criticism of –amongst other things – religion, alternative medicine and the monarchy. This time, he addresses tensions on Turkish schools in the Netherlands between supporters of president Erdogan and supporters of the cleric Gülen, whose movement allegedly staged the 15–16 July coup d’état attempt in Turkey, and is currently facing governmental repression that has repercussions in other countries.

In an information video by a fictional school addressed to teachers, Lubach says that, to reduce tensions amongst pupils with different backgrounds, several measures have been taken, including:

In case of an emergency, pupils will be informed by telephone. (…) Jewish pupils don’t need to be called, they’ve already heard everything through the Zionist conspiracy.
Not all pupils have been raised with the same ideas about history. Therefore, different truths apply in different areas of our school building. The hallways have been equipped with different colour codes:
– In hallways with a green stripe, the Holocaust never took place;
– The Armenian Genocide is denied in the red zone;
– And if you see wallpapers with flowers, 9/11 is an inside job.