Why does Holden misinterpret Mr. Antolini's message?

Holden tends to misinterpret or dislike the behavior of adults in general. Though The Catcher in the Rye was published in the early 1950s, Holden's personality is a kind of prototype of the stance young people generally adopted in the next decade, the 1960s, that one should "never trust anybody over 30." His attitude to the teacher Spencer is typical, as he somehow even resents Spencer's calling out "Good luck!" to him when he leaves. He thumbs his nose at the adult world in little ways as a private rebellion—for instance, when he tells the woman on the train that his name is "Rudolf Schmidt." One needs to observe as well that Holden is hostile to and mistrustful of even most people his own age. He envies and hates the "athletic bastards" like Stradlater and finds even the pathetic Ackley dislikable.
Mr. Antolini is one person who seems genuinely to care about Holden and to attempt to get through to him and give him some help on his life's journey. Part of the problem to begin with in Holden's interaction with him, however, is that Mr. Antolini appears to be drunk or at least buzzed. His advice is well-meant but somewhat incoherently given, and Holden's dislike of all adults comes through in the way he reports and comments inwardly on Antolini's words to him. When Holden wakes up and finds Mr. Antolini patting him on the head and saying he is "admiring" him, Holden concludes that Mr. Antolini is gay, and that's that.
Throughout Catcher in the Rye, Holden makes various derogatory references to gay men, calling them "flits" and generally saying negative things about them. (Interestingly, when I first read the book in the 1960s, I had never before—and have never since—heard the term "flit" among the plethora of derogatory words then used about gay people.) It is unclear whether Salinger is presenting Holden's attitude ironically, is endorsing it in some way, or is simply reporting it as "normal" for the time. Unfortunately for the episode dealing with Mr. Antolini, both his apparent drunkenness and this gesture interpreted by Holden as an "advance" make it impossible for Holden to bond meaningfully with Mr. Antolini and accept his advice.