He may dislike it because he feels that it undermines the real struggles and achievements of the ninja. In fanfiction, things might be made too easy or unrealistic. He has fought tooth and nail for everything in his ninja life, and seeing it made into something that doesn't represent that in fanfiction would make him hate it.
One reason could be jealousy. If in the fanfic, Sakura gets closer to someone else Naruto cares about, like Sasuke in a different way than he expected, it might make him hate her. For example, if Sakura teams up with Sasuke against Naruto's wishes in the fan - created plot.
One possible reason could be jealousy. Maybe in the fanfiction, Jiraiya gives more attention to another character, and Naruto, being young and impulsive, starts to hate him for it.
Perhaps he has seen fanfiction that contains inaccurate information about the Naruto universe, such as wrong jutsu descriptions or incorrect interpretations of the ninja clans. This would make him dislike it as he is an educator in the Naruto world and has a certain standard for knowledge about it.
One possible reason is a misunderstanding. If there are rumors or false memories planted in Naruto's mind, he might believe his mom did something unforgivable. For instance, if he's made to think she was involved in the death of someone he cared about.
In some fanfics, there could be a misunderstanding. Suppose Kushina did something that Naruto misinterpreted as harmful to him or his friends. This misinterpretation could lead to his hatred. For example, if Kushina was involved in a mission that Naruto thought put the village at risk, but in reality, she had no choice.
In some cases, the fanfiction might be a crossover with another universe where the idea of a ninja doesn't fit. So, to make Naruto fit into this new universe, the writer has to take away his ninja identity. This allows for new and interesting interactions between Naruto and characters from the other universe.
One possible reason is that the person may find the fan - made interpretations of the Pokemon world too far - fetched. For example, some fanfictions might give Pokemon abilities that are completely against the established rules in the official games or anime. This can be off - putting to those who like the consistency of the official lore.
Well, it could be related to the secrecy and mistrust that often surrounds those with great power in the ninja world. Naruto had the power of the Nine - Tails, and the village elders may have spread some misinformation or negative views about him to keep the situation under control. This misinformation could have led some villagers to hate Naruto. Additionally, Naruto was a bit of an outcast in terms of his social skills when he was young, and his loud and boisterous nature might not have been well - received by the more reserved villagers, contributing to the hatred.
One possible reason is that the fanfiction distorts the original relationship between Bella and Sam in a way she finds unacceptable. For instance, if it creates a false romantic tension where there shouldn't be one.
It could also be that in the fanfiction, Percy is given a new power or ability that Annabeth sees as a threat. Or perhaps Percy is made to side with someone Annabeth dislikes, causing her to 'hate' him in that fan - created story. This shows how different plot elements in fanfiction can change the dynamics between characters.