One possible reason could be a misunderstanding. Maybe some false information was spread within the fanfic about the Uzumaki clan that made Naruto believe they were bad. For example, if there were lies about his family's past actions that he wrongly thought were true.
Another reason might be related to a specific event in the fanfic. For instance, if the Uzumaki clan was somehow involved in an incident that led to the death of someone Naruto cared about, even if it was by accident or misjudgment. He could then develop hatred towards the clan out of grief and anger.
One possible reason could be that he feels burdened by the expectations associated with the Uzumaki clan. Maybe he doesn't like the constant attention or the pressure to live up to the clan's legacy.
One possible reason could be some sort of dark secret within the Uzumaki clan that Naruto discovers. Maybe it has something to do with the clan's past actions that go against his moral code.
In the fanfiction, it could be that Naruto has had some personal negative experiences with Uchiha clan members. He might have witnessed some Uchiha using their power to bully or oppress others. Naruto, being the kind - hearted person he is, would not tolerate such behavior and thus develop a hatred for the clan as a whole. This could also be related to the Uchiha's reputation for being a bit of an outcast clan, and Naruto might see them as not fitting into the harmonious village life he envisions.
It could also be because of the Uchiha clan's perceived aloofness. The Uchiha might seem standoffish and exclusive, which could make Naruto, who values friendship and community, dislike them. They may have a reputation for being more concerned with their own clan's affairs rather than the well - being of the whole village.
Maybe the clan heads have been unkind or unfair to some of Naruto's friends or people he cares about. If they've shown discrimination or harsh treatment towards those without strong clan ties, Naruto, being empathetic, would likely develop a dislike for them.
It could also be due to a clash of personalities. The Inuzuka clan has a very distinct and often aggressive way of approaching things, with their strong bond with their ninja dogs. Naruto, with his more free - spirited and sometimes impulsive nature, might find their ways irritating and over time, this could develop into hatred.
Perhaps there were some dark secrets in his clan that he discovers. These secrets could be related to past wrongdoings, like how they treated other clans or individuals. If Naruto has a strong sense of justice, learning about these things might make him hate his clan. It could also be that he feels ostracized or different within his clan, like if he has abilities or beliefs that are not accepted by the majority of the clan members.
It could be that the fanfic portrays Hinata as being arrogant towards Naruto's past. Naruto has had a difficult childhood and if Hinata in the fanfic mocks or belittles that, it would make Naruto hate her. For instance, if she scoffs at his time as an outcast in the village and uses it as a means to elevate herself, Naruto would surely despise her for it.
One possible reason could be that he feels neglected. Maybe his family was always too busy with other things and didn't give him enough attention. This lack of attention during his formative years could have led to feelings of resentment.
Maybe in this fanfic, there has been a misinformation spread about Naruto that makes Kushina believe he has done something unforgivable. For example, if false rumors say that Naruto is involved in something evil, Kushina might start to hate him without knowing the truth.