One reason could be a misunderstanding. Maybe Harry said or did something that his friends misinterpreted. For example, if he was overheard making a comment that seemed critical of them but was actually taken out of context.
The simplest explanation was that when a person made a decision or action, he paid more attention to the things on the left and ignored the things on the right. This idiom can also be used to describe a person who only takes one aspect into consideration when dealing with a problem and ignores other aspects.
Naruto could ignore fanfiction because it often contains elements that are not part of his reality. The fan - made stories might distort his character or the relationships he has. For example, some fanfiction might pair him with characters in a way that doesn't make sense to him or goes against his values, so he just ignores it.
I don't quite understand what your question means. Can you provide more context or information so that I can better understand your question and provide you with a more accurate answer?