Some people are attracted to groups where the requirement to join is the acceptance of the "truth" of a readily disprovable claim. They are all comfortable in their complicity and a world that might not be flat, but is certainly divided into an "us" and "them". They are comfortable with the knowing avoidance of certain questions, topics, materials, logic. This might be the curvature of the earth visible in an airplane ride, fossils, or any other uncomfortable source of contradiction. These beliefs and the people can become dangerous if unchallenged. Cults and certain political movements are examples of this. I will leave it up to the reader to decide on examples.