Some writers might want to explore a different side of Naruto. Maybe they are tired of the same old positive - friendship - based stories and want to create a more edgy or dark take. They could be exploring what would happen if Naruto had a falling out with his friends due to some external factor like a power struggle or a betrayal that he wrongly perceives.
Perhaps in the fanfic, there is a prophecy that says Naruto's friends will be the cause of his downfall. So, Naruto, fearing for his future and the safety of the village, starts to distance himself from them and eventually hates them. Or maybe his friends accidentally cause the death of someone Naruto loves dearly, which makes him unable to forgive them.
The story could also take a darker turn. Ash's hatred for his friends might lead him to team up with villains in the Pokémon world. He could use his knowledge of his friends' weaknesses to help the villains, creating a big conflict. And his friends would then have to figure out how to stop Ash and get him back on the right side.
Maybe in the fanfiction, his friends keep getting in the way of his goals. For example, if Ash is really focused on becoming a Pokémon master and his friends are constantly causing distractions or making him take detours from his training and battles.
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.
It can be quite divisive. Some fans might be extremely offended as Naruto is a beloved character known for his positive traits. This type of fanfiction goes against the established character arc and values. It could make some fans angry that someone would distort Naruto's character in such a way.
One possible reason could be that Naruto is afraid of endangering his friends. He has many powerful enemies, and he might think that by staying away from his friends, they won't be targeted. For example, Orochimaru was always after Sasuke, and Naruto might fear that his closeness to Sasuke could put Sasuke in more danger.
It could be that the 'mother love' in the fanfiction goes against Naruto's own ideals or his perception of family. Naruto grew up without his parents, and if the fanfiction presents a mother love that is forced or not in tune with his experiences, he might hate it. He has his own understanding of love and family through his friends and the village, and this fanfiction concept could be a jarring deviation from that.
One way could be through Naruto feeling neglected by his family. Maybe in this fanfiction, his parents were alive but were always too busy with village affairs, leaving Naruto feeling alone and unloved. This could lead to his hatred as he grows up seeing other families being more present for their kids.
One possible reason could be jealousy. Maybe his brother has some special abilities or gets more attention that Naruto feels he should have. For example, if his brother is really good at a certain jutsu and is always praised for it while Naruto struggles, that could lead to resentment.