As an ex-fundigelical, I think the boys get it wrong here. Perhaps the people at the top are cynical with regard to the existence of demons, but I guarantee there's a concerning number of people in the crowd who think demons are real, and they genuinely think they're fighting a holy war against them by opposing people that include "liberals and 'unhuman' communists." I used to think demons were actually real, and average people often had demons inside them, like sleeper agents waiting to be activated.
I agree that the "demonic" rhetoric is a convenient tool to justify political violence, but many of them aren't using demons as an excuse to do something they already want to do; they're doing it because they genuinely think they're saving humanity from Satan to usher in some kind of idealized 1950s utopia ~~only for white, affluent Christians.~~
In their mind, they are sincerely at war with their fellow Americans, but there's a convenient, dehumanizing layer of "demons" to make them feel better about any acts of violence or stripping of rights.
Hello, spectre of Nazism.