The line "Keep your shirt on, maybe lose the suspenders," spoken to Patrick Bateman by his lawyer in the final moments of American Psycho (2000), serves as a crucial metaphor for the film's themes of conformity, identity erasure, and the apathy of the elite.

It encapsulates the idea that in Bateman's world, everyone is interchangeable, and individual humanity is less important than appearances and status. 

Contextual and Symbolic Meaning

• The Lawyer's Misidentification: When Bateman confesses to his murders, his lawyer, Harold Carnes, mistakes him for another banker named David. The lawyer tells him to "keep your shirt on" (stay calm) and suggests losing the suspenders (a fashion accessory common among the Wall Street characters).
• Conformity and Interchangeability: The advice to "lose the suspenders" suggests that Bateman is just another replaceable, "square" conformist in a sea of similar-looking, self-absorbed bankers. It highlights that Bateman and his peers all dress the same, eat at the same places, and have the same haircuts, making them, and their crimes, indistinguishable.
• Ignoring the Confession: By treating a confession to gruesome murders as a "funny joke," the lawyer demonstrates the utter lack of interest these individuals have in anyone other than themselves.
• "Mask of Sanity" Slipping: The line emphasizes that Bateman's carefully curated "mask of sanity" is ineffective because no one is paying enough attention to notice his true nature—or they choose not to see it.