A cult is what you make of it.

The first novice, Ni no Tachi, was not a cultist. The key was Ougi's statement: "How long will you repeat my words and ignore the meaning?"

Ni no Tachi learned the meanings and became a true rationalist - he understood that the clothes had nothing at all to do with it. You could kind of think of them as a way of promoting group identity while weeding out those destined to be forever irrational.

Bouzo never even got to the key statement. He stopped questioning as soon as Ougi implied that the silly hat was necessary. He learned all the teachings of Ougi, but he never understood their meanings. Eventually he would only discuss rationality while wearing a clown suit, because he believed without any evidence that silly clothes were related to probability theory, which is completely irrational.

Bouzo was a cultist.