Holden judges and hates nearly everyone, but he’s also super lonely. Hm. Conundrum. We see the same scene play out over and over: (1) Holden meets a person; (2) Holden judges the person to be a "phony," a "moron," or a "pervert"; (3) Holden tries to reach out to that person anyway, usually by asking them to have a drink with him; (4) the person refuses.
All the people Holden attempts connections with are similar in this way, so they're all foils for one another. To be specific, we're talking about Ackley, Mrs. Morrow, nameless cab driver #1, Faith Cavendish, Bernice, Marty, Laverne, cab driver #2 (a.k.a. Horwitz), Sunny, the two nuns, Sally, the little girl with the skates, Carl Luce, Valencia, Valencia's piano-player, the hat-check girl, the secretary at Phoebe's school, and, you know. Pretty much every single other minor character.
The scenes that play out between Stradlater and Holden and then later between Maurice and Holden are foils for each other. In each instance, Holden is wronged, forces the issue, is threatened, given an opportunity to back down from a much stronger opponent, cries, insults the much stronger opponent's intelligence, and ends up getting socked. We think these two scenes are getting at Holden's self-destructive tendencies. You know, just maybe.
The Holden-Spencer conversation and the Holden-Antolini conversation mirror each other structurally—they're the book-ends to the novel, so to speak, one at the very beginning, one near to the end. Both feature a former teacher berating Holden for not taking education seriously. Both revolve around a strange physicality: with Mr. Spencer, Holden’s gross-out awareness of the man's body and its appearance; with Mr. Antolini, the gross-out (to Holden) contact between the two characters.
But being foils and all, there are some differences, too. Mr. Spencer's lecture is an alienating and actually rather annoying rant. Mr. Antolini, on the other hand, actually has some real insight into Holden's character, and some real advice to offer him. Are the two teachers very different, or has Holden evolved over the course of the novel so much that he's now able to hear and accept help instead of rejecting it—and therefore presenting it to us—as phony and irritating?