One possible reason could be a misinterpretation of family dynamics. Maybe in the fanfiction, the author portrays Naruto's family in a way that he sees as unfair or unloving. For example, if they are shown as neglecting him or putting too much pressure on him.
It could also be due to some major changes in the family's story in the fanfiction. Perhaps his family is involved in actions that go against Naruto's values. Like if they are made to be part of a corrupt system that Naruto hates, so he loathes them as a result.
On the other hand, it could also spark interesting discussions. Fans could debate about whether this new take on Naruto's family is valid or not. It might even inspire some fans to write their own counter - fanfictions to restore the positive view of Naruto's family.
In the fanfiction, it might be that Naruto had different ideals and goals from his family. His strong will to pursue his own path of becoming Hokage, for example, could clash with the family's expectations, causing him to reject them.
Perhaps Naruto has some unresolved issues from his past that he doesn't want to burden his family with. He may think that leaving is the best way to deal with these issues on his own, without putting his family in the middle of his personal turmoil. He might go off on a solo adventure to find himself and come to terms with his inner demons.
Perhaps there were secrets in the family that Naruto discovered. In fanfiction, it's common to introduce hidden family secrets. If Naruto found out something like his family having a connection to an old enemy or some dark past, he could be angry and snap at them.
One possible reason could be a misunderstanding. Perhaps Naruto misinterprets some of his family's actions or words. Maybe he thinks his family didn't care about him as much as he thought they should. In fanfiction, authors often play with the idea of miscommunication and how it can lead to strong negative emotions like hatred. Also, if there are other characters in the fanfiction who influence Naruto's view of his family, say by spreading false rumors or manipulating him, that could contribute to his hatred.
One possible reason could be a long - held misunderstanding. Maybe Naruto discovers some family secrets that he misinterprets as betrayal or neglect. For example, if he finds out that his family had made some sort of pact that he disagrees with, it could lead to his rejection.
One possible reason could be that he has some unresolved issues from his past, like the absence of his parents during his childhood which made him feel a sense of detachment. Maybe he is so focused on achieving his ninja goals that he unconsciously starts to ignore his family. Another reason might be some sort of miscommunication within the family. For example, if there are secrets that the family has been keeping from him, he might feel betrayed and thus choose to ignore them.
His family might have neglected him in some ways. Naruto grew up alone and feeling unwanted in the original story. If in the fanfiction, his family was around but still didn't give him the love and attention he needed, it would be a valid reason for his anger. He has always craved connection and acceptance, and if his family failed to provide that, he would be furious.
Another reason might be related to family politics. In some complex family structures in the Naruto universe, there could be different factions. Naruto might be on the wrong side of the power struggle within the family. His views or actions could be seen as a threat to the traditional power structure of the family, so they hate him.
One possible reason could be a series of misunderstandings. Maybe his family made decisions that he felt were against his principles or dreams, and after repeated attempts to reconcile the differences, he just lost hope. For example, if his family was against his ninja way, which is such a core part of his identity.