Catcher in the Rye- Chapter 22

Holden goes back to Phoebe's room and gets her to listen. He attempts to explain why he is failing most of his classes and starts listing all the things he hates about school. Phoebe's response is accusing him of having hate for everything. He objects, but she pushes even more by telling him to name one thing he likes and he becomes distracted. Thinking about the nuns at breakfast and James Castle. James was a boy who jumped out of a window, at Elkton Hills School, while being teased by other boys. Holden finally tells Phoebe that he likes Allie and she reminds him that Allie is dead. She starts asking what he wants to do with his life and the only thing he says is "If a body catch a body comin' through the rye." Holden says he wants to be the catcher in the rye. He wants to catch children if they get too close to a cliff's edge. Phoebe says Holden had heard the words wrong.

Did something so simple like a little song/poem inspire Holden so much? Was that kind of a turning point in his life?