The phrase "pure lunacy" means something that is completely crazy or nonsensical. It refers to actions or ideas that are so absurd or irrational that they seem like the result of madness. Full definition
jesus was a thief and a lier, anyone who puts there faith in him is nuts... and that joe smith guy — thats just pure lunacy! (religion.blogs.cnn.com)
Better still, he scrubs his film free of smarm and superiority by extending the tired components of the sports flick past the point of satire into a realm of pure lunacy: For instance, the romantic lead needs a villainous, dislikable fiancée to stand between him and the true love interest. (thedissolve.com)