Mr. Antolini is Holden's former teacher--"the best teacher I ever had"--at Elkton Hills. Bored and lonely, Holden decides to call him late one night, and Antolini graciously invites him to his home. Antolini and his wife had hosted a party earlier in the evening, and he appears to have been a bit drunk. The two reminisce, and Holden complains about teachers at Pencey. Antolini defends their actions, and writes a note for Holden to consider.
"The mark of the immature man is that he wants to die nobly for a cause, while the mark of the mature man is that he wants to live humbly for one."
It is a reflection to consider, but Antolini appears to have misdiagnosed Holden, who certainly has no beliefs in which he feels strongly enough to die for. After Antolini prepares his couch for Holden's bed, Holden goes to sleep; but he awakens to find Antolini rubbing his head in the dark. Holden--rightly or wrongly--interprets Antolini's affection as a homosexual overture, and the boy quickly exits the apartment in the dead of night.
When a handsome sixteen-year-old boy spends several days and nights wandering around Manhattan, he is bound to have encounters with homosexuals. Salinger undoubtedly felt that he had to have at least one such incident for the sake of verisimilitude, just as he must have felt that his novel needed to include at least one episode involving a prostitute. Mr. Antolini might be said to represent the homosexual aspect of New York City, just as the young prostitute called Sunny might be said to represent the aspect of commercial heterosexual vice. The readers of "The Catcher in the Rye" found these two episodes shockingly racy when the book came out in the late 1940s, but they seem pretty commonplace to contemporary readers.