How does the theme "accepting others for who they are" appear in the book A Separate Peace?

In chapter 4 of A Separate Peace, Phineas and Gene argue about their differences rather than embracing them. The argument arises when Phineas wants Gene to stop studying and go for a swim with him. Gene already feels jealous of Finny's charisma and athleticism, so he feels burdened to have to always do what Phineas wants to do. It seems as though Phineas is jealous of Gene's academic achievements and Gene is jealous of Finny's athletic ones. If they simply had accepted each other for who they are, they could have avoided the next scene where Gene jounces his friend out of the tree and breaks Finny's leg. Because of this tragic incident, Phineas loses the ability to be an athlete and they both must accept the reasons behind the accident--an unaccepting nature and jealousy. 

Gene admits responsibility for breaking Finny's leg in chapter 5, but Phineas can't accept that his best friend would do something like that on purpose. As a result, they both live in denial about Gene having been ugly to his friend and Finny being forced completely out of sports, and out of the war, forever. It isn't until Phineas breaks his leg again in chapter 11 that the boys are forced to accept each other and themselves completely. For example, once Phineas breaks his leg for the second time, it is closer to the end of his senior year and the time when he would be allowed to enlist in the military. This second break drives home the reality in Finny's mind that he is too injured to go fight in the war--something he really wanted to do. Then for Gene, the second break allows him to revisit his responsibility for the first break with his friend. He and Finny both have to accept the ugliness Gene felt inside that forced him to jounce the limb like he did. Finny says the following about Gene's state of mind at the time:

"It was just some kind of blind impulse you had in the tree there, you didn't know what you were doing. Was that it?" (191).

Gene claims that Phineas analyzed the situation correctly, but that he is also very sorry about it all. Phineas shows a merciful and generous nature by forgiving Gene for breaking his leg. As a result of this final conversation between the boys, they are each able to accept each other as well as themselves for the mistakes. It is alway so much better to accept others (and ourselves) for who they are; otherwise, we are bound to make mistakes and presumptions that cause everyone unnecessary drama.