The Black Panther Party was a progressive movement that fought for civil rights using any means necessary. It was targeted by the FBI. Their idea of "revolutionary suicide" was co-opted by Jim Jones, who, though white, proclaimed to tout the ideals of the Black Panther Party (though he did not). The Black Panther Party's famous members include leader Huey Newton and Stokely Carmichael.

To establish distance from the negative connotations of the word “cult,” Montell coins this term to mean that which is cultlike or exhibits the traits of a cult, particularly through language. While the book addresses cults directly as well, it uses the concept of “cultish” to explore more ambiguous rhetoric and techniques of groups seeking followers.

Confirmation bias is the idea that people will seek out, retain, and filter information that reinforces their preexisting beliefs, while tuning out the rest. Confirmation bias features prominently in Part 2, Chapter 10, in a discussion about participants in cultish groups being more likely to see leaders as speaking to ideals they believe in while being able to ignore the rest.