Explain Holden's sudden lack of maturity, with comments like, "stupid moron".

By Chapter 6, Salinger has established that Holden suffers some great psychological difficulties, yet knowledge of these instances come from secondary sources. But in this chapter, Salinger brings Holden's unpredictable behavior clearly to the fore. Holden behaves almost solely on impulse, even when there seems to be no rational motivation for his behavior.

As this chapter demonstrates, this inability to control his behavior reaches far beyond any normal teenage impulses, as shown when Holden rips up Stradlater's essay when he fails to appreciate Holden's work. The fight between Stradlater and Holden also shows Holden's inability to control himself; when he suspects that Stradlater has slept with his old friend, Holden responds by punching him.

This event reveals contradictory impulses within Holden. Although he claims that he is a pacifist, a dubious statement that reinforces his status as an unreliable narrator, Holden seems disconnected from the violence he causes and the pain that he suffers. He views his fight from a distant perspective, appreciating the look of his bloody face without considering the actual fight itself. This predilection for extreme behavior and lack of connection to his own actions will be a consistent theme throughout The Catcher in the Rye, as Holden continues to allow his behavior to reach disturbing extremes. Indeed, The Catcher in the Rye, for all its apparent episodic nature and aimlessness, actually follows a pretty traditional structure, complete with intensifying rising action, leading to a climax, and then ultimately a denouement.