Hello there!
Im just gonna clear a few things up about dipper, because now i realize how badly written dippers reason for hating Cody was:
Dipper knew that Mabel liked Cody (like a brother) and he didn't want her to be divested if/when Cody had to go back to his demention (sorry i spelled it wrong)
He thought Cody might be a traitor and didn't want mabel to be there if he was, so he "protected" her from Cody, thinking  it was better for Mabel to think he was a traitor than someone else she lost.
He never hated Cody, he just hated that his sister felt like he was her brother because he felt like he was being replaced and shut out.
Well, thats it! BBBBYYYYEEEE!!!