You need the "is of identity" to describe conspiracy theories. Korzybski would say that proves that illusions, delusions, and "mental" illnesses require the "is" to perpetuate them. (He often said, "Isness is an illness.")
Korzybski also popularized the idea that most sentences, especially the sentences that people quarrel over or even go to war over, do not rank as propositions in the logical sense, but belong to the category that Bertrand Russell called propositional functions. They do not have one meaning, as a proposition in logic should have; they have several meanings, like an algebraic function.

Language as Conspiracy, p. 277 - Everything Is Under Control (1998)