"Behaviorism tells us that all behavior is unique: there are no underlying processes or objects driving the various behaviors we perform. While behaviors may cause other behaviors, a behavior is ultimately at either end of this causal chain. This destroys the basis of all psychoanalysis, and while the observations may possibly still hold, any and all interpretation or theory is meaningless. Freud and his followers were chasing an illusion."

Well, what are behaviors? Many-a-times they are expressions mental states, hence enabling us to infer some sort of conclusion upon a particular person's mental state by observing their behavior; I'm failing to see how this undermines psychoanalysis.