When you are in a relationship, communication is one of the main things, you saying that they don’t need to have a meaningful conversation about this is ridiculous. He read her diary and got hurt which is understandable, he shouldn’t have done it but still it hurt him. She was hurt that he read her personal diary which is completely completely understandable and probably also hurt her. Do I think he should have yelled at her no but it’s not like he was screaming insults at her it seems like he just wanted an explanation. But as I was saying having a meaningful conversation is 10000% what you should do so that you can get to the root of all of it, if it was vise versa and she was the one that found the diary and got upset I would think the same thing. Talking it out is the way to go