Because he loved her. A lot. At the time he was a kid when she did it to him and he didn’t really understand what was happening. And she didn’t molest him and be a complete asshole to him every other second. She was kind to him and he really loved her, that much is evident through the whole story. And he was angry with her when he finally found out what happened but he chose not to blame her.

“And we could all sit around and wonder and feel bad about each other and blame a lot of people for what they did or didn’t do or what they didn’t know…It’s like if I blamed my aunt Helen, I would have to blame her dad for hitting her and the friend of the family that fooled around with her when she was little. And the person that fooled around with him. And God for not stopping all this and things that are much worse. And I did do that for a while, but then I just couldn’t anymore. Because it wasn’t going anywhere. Because it wasn’t the point.” (p. 210-211)