I think it's similar to what Thomas Frank describes in his earlier books, about how popular culture coopts and neuters potentially revolutionary or subversive ideas.

In this case, it's the Enlightenment philosophy of progressive secular humanism being appropriated by regressive forces of animality, or by so-called conservatives who are servants of their selfish, evolutionary instincts, avatars of their mindless genes, and who thus roll back progress to reestablish the dominance hierarchy in human societies.

They redefine "liberty," hollowing out the concept to make it consistent with their social Darwinism.

The Catholic Church did this for centuries in its Christianization of Greek philosophical concepts, such as Logos. Ironically, the US tamed or Americanized even that bastardized Christianity, giving us the multiply corrupted form of Evangelical Christendom that cheered for "President" Trump.