I'm going to start off with this disclaimer: yes, Holden is a self-entitled brat. He's an overly emotional, thoughtless wreck of a person who doesn't think through his actions, inconveniences and makes snap judgements about everyone while also hypocritically doing the same things he claims to despise. He is probably one of the most unlikeable protagonists ever.
But I can’t bring myself to hate him.
We know from context that Holden is a middle child and is largely either ignored or seen as a disappointment by his mostly absent parents. And I think that’s a big thing to consider when looking at all of his outlandish actions and thoughts. I can't imagine how isolating it must be to be the "bad one" in the family, the one who's told he isn't trying hard enough and that he doesn't have any prospects in life because he isn't trying hard enough by even the teachers he respects. How much must it hurt to remember Allie and how amazing he was while (to Holden) the rest of the world got over it and moved on? It got me thinking how awful and dehumanizing that must be, to be the child who fails over and over and over again and is told that it's something inherently wrong within himself that he needs to fix when he doesn't even know what that something is. How desperate must he be for any kind of authentic attention or reaction (be it positive or negative) from any adult in his life? Rather than just receiving a stern lecture and being told he needs to be shipped off to another school and retry applying himself, I think Holden just wants more than anything (like most people) to be seen and understood and loved.
He tries so hard to "play" at being an adult, almost like how a little kid plays house. He (very badly) imitates their behaviors, social cues, and conversational skills because he wants to prove how "phony" it is. But every time he tries this, he ultimately fails because he can't bring himself to understand the complexity of adult life. He doesn't want to because he's afraid that if he begins to grapple with it and understand it, then he's going to have to leave behind all of that joy and simplicity that he remembers childhood to be.
Because under all that swearing and smoking and false bravado, there's a kid who just lost his little brother a few years ago and doesn't know how to handle it. Under all of it, there's a scared little kid who's afraid that he's going to lose himself if he grows up. Under all of it, there's a little kid who's sick and needs help because he just spent three days on the streets of New York in winter all alone. There's the kid who buys his little sister a record because he wants to make her happy and cries because the poem that he treasures dearly and has emotional investment in is just a misrememberance. There's the kid who erases expletives on school walls because he doesn't want little kids to see it. There's the kid who buys his sister a ride on the carousel because he doesn't want her to be scared or mad at him. #entertainment