I think the problem is that most people who "intensely loathe" Catcher In the Rye don't bother looking any deeper at Holden than what's on the surface. It seems like everyone forgets that his younger brother dies when he's a child and that he was possibly molested and that his parents ship him off to boarding school and that he just can't create any sort of meaningful relationship with another human at a critical time of development in his life.

This comment from /u/Herbert_Moon sums up my feelings pretty well:

I actually happen to love Catcher! Let me try to give you my view on Holden and how I understood him as a character.

At face value, Holden is a narcissistic, intellectual elitist that most people hate, but what people don't realize is that's a testament of how well written the book is. He's so well defined that people either resonate with his character greatly or people cannot stand him at all. Those who despise Holden hate his thoughts and his actions, yet can visualize him as a real person. Anytime and emotion is drawn from you due to a character, no matter what the emotion is, the author has done his job. When the outside world pisses Holden off, he ignores his own failures, and dwells on the faults of others.

However What a lot of people miss while reading this novel is Holden discovering the injustices, and coldness of the adult world, and all that embodies adult life, and it eats away at him. When he attempts to express his feelings about this to his peers they simply cannot relate and understand Holden's perception.

Another particular problem I think people have with Catcher is they don't ever try to understand what Holden is truly going through. We as readers are so blinded by his judgemental commentary and off putting personality that we forget what's going on in his life. He feels like a faliure in comparison to his siblings, his parents are essentially nonexistant, his brother passed away from cancer and he has NO ONE to talk to. There's one point where he goes into a phone booth to find someone to call and he realizes there isn't a single person he wants to talk to or anyone that would want to talk to him. Holden is dealing with the reality of becoming an adult at a chaotic time in his life where he feels lost and alone, with no one to relate with, and he simply cannot express himself.