Maybe it's because they come from different fictional universes with very different values. Naruto is from a world of ninjas where loyalty to the village and personal growth through hard training are emphasized. Erza is from Fairy Tail with a more guild - centered and magic - based world. Their different outlooks and ways of doing things might clash in the fanfiction, leading to Naruto's hatred.
Perhaps it's a plot device created by the author to drive some kind of conflict. The author might want to create a unique and unexpected scenario where two popular characters from different series dislike each other. This can add drama and tension to the fanfiction, and Naruto hating Erza is just a way to start that interesting story line.
It could be that Naruto has a different view of leadership than Sarutobi. Naruto might see Sarutobi's leadership as being too passive or too focused on maintaining the status quo. He, with his more energetic and revolutionary ideas, may resent Sarutobi for not being more progressive in making the village a better place for everyone, including himself.
One possible reason could be a misinformation plot. Maybe in the fanfiction, Naruto has been led to believe that Yondaime had some dark secrets or did something bad to his family that he discovers later in the story.
Perhaps Naruto feels that the Hokage has been too strict or unfair in dealing with certain situations. Like if the Hokage didn't support Naruto's way of trying to bring peace and unity, which Naruto firmly believes in. This could lead to a growing resentment and eventually hatred.
One possible reason could be a feeling of betrayal. Maybe the Kages made decisions that Naruto thought were against the greater good or the well - being of the ninja world. For example, if they were too focused on protecting their own villages at the expense of others.
Perhaps he blames ninjas in general for the loss of someone close to him. For example, if a group of rogue ninjas were responsible for the death of a dear friend or family member, it could make him resent the whole ninja concept. He might think that if there were no ninjas, such tragedies wouldn't occur.
One possible reason could be betrayal. If Naruto was constantly let down or betrayed by those he trusted among humans, it could lead to his hatred. For example, if his friends turned on him because of his jinchuriki status.
One possible reason could be a misunderstanding. Maybe Anko was involved in a mission that Naruto thought was unjust, and he misjudged her actions as being malicious. For example, if she had to capture someone Naruto considered a friend, even if it was for the right reasons from Anko's perspective, Naruto might hold a grudge.
Maybe they could be rivals at first. Erza is highly competitive, and Naruto is always looking to prove himself. Their initial rivalry could turn into respect as they see each other's skills in combat. For example, Naruto might be impressed by Erza's ability to change armors and use different types of magic, while Erza could admire Naruto's never - give - up attitude and his powerful jutsu.
One possible reason could be that Naruto discovers some long - hidden secrets about Minato that he feels betrayed by. For example, if he found out Minato had made a deal that affected Naruto's life negatively in some way, like with the Kyuubi. Maybe Naruto feels that Minato sacrificed him for the greater good of the village without really considering his future or feelings.
Perhaps in this fanfiction, Naruto has been influenced by some external force. It could be a dark entity that has corrupted his view of Team 7. He might see them as a hindrance to achieving some greater, more self - centered objective. Also, it could be that Naruto has had some sort of personal revelation about his past and blames Team 7, or certain members of it, for things that he now believes held him back in the past.