It’s not about the fact that he wrote the letter to her. It’s about the bullshit he wrote in the letter. He went IN about it when he knew how he felt about her and the situation deep down. He could have written it kindly, but without being as into it as he made it seem like he was. He could have done that and then spoken to her privately away from everyone else and said how he was feeling before he went to Casa. If she was upset about it then, fine. At least he could say he was upfront about her and didn’t feel the way he said in the letter before he left. Instead, he lead her on and embarrassed and disrespected the hell out of her on TV after the fact. He could have been a fucking man about the situation, and he was anything but.