The thing that always perplexed me is why did Bateman hesitate in killing the ginger after he expressed he was gay for him?
When I first seen it, I thought it was building up to the ginger (Luis) being the
real Patrick Bateman and that the Patrick we saw, was just an invented persona, aided by the fact that Patten, Allen and Bateman look
very closely alike, they could be mistaken for the same person or be seen as brothers.
And I guess them looking similar is sorta the point, to add to the credibility that the lawyer at the end could genuinely not tell people apart, but the Bateman persona could've been based off people Luis is surrounded by and who look much more confident and sharp.
I guess the theory still holds some weight, it would explain why Bateman didn't kill Luis, especially since he had no reservations about killing random homeless people, why would he in any way tolerate some pale ginger man kissing his hands, leaving him clearly disgusted? Maybe it was Luis confronting himself, with his authentic self being very grateful and infatuated with the persona, while his persona side being utterly disgusted at what kind of a gay wimp he his at heart.
It would also add context to the notebook at the end, which is filled with childish drawings of with cartoonish and unrealistic murders like... dropping a chainsaw down the stairs and miraculously hitting the woman at the bottom... and of course, that ATM demanding the death of a kitten. Whether or not any deaths were real is already debated, but with the film itself functioning as an unreliable narrator (we never had any monologues of Bateman describing the murders, only his life routine. The only exception is the confession, which may address murders that didn't happen) it does leave room to the idea that the Bateman we see may not be real. That not only the murders, but the whole persona is made up in someone's head.
It would also explain why the lawyer took Bateman's confession as some dumb joke, maybe he was actually talking to Luis and the very idea that somebody like Luis could ever commit mass murder was so ludicrous to him, he continued viewing it as some kind weird joke.
Ok, as I continue writing this, I'm beginning to realize I should've written this down sooner, I presumed that it was silly and wouldn't have much to it, but I'm actually having fun reinterpreting the movie in this way!