Well, it could be that in certain fanfics, the writer is trying to create a new and different storyline. Harry hating Gryffindor could be a way to introduce conflict. For example, if there are issues within the Gryffindor house that Harry doesn't agree with, like unfair treatment among students or a power struggle among the prefects. This could lead to his dislike for the house.
In some fanfics, Harry might be made to hate Gryffindor perhaps because the author wants to explore an alternative personality for him. Maybe they want to show how the Gryffindor house's values, like bravado or recklessness, could be seen in a negative light from Harry's perspective.
Perhaps Harry has his own vision of Gryffindor and the fanfics he's seen don't align with it. He might have a deep - seated understanding of what Gryffindor means to him, like courage, loyalty, and friendship in a very personal way. The fanfics, on the other hand, might focus on more superficial or inappropriate aspects of Gryffindor for his taste, such as focusing too much on power plays or false bravado rather than the true essence of what makes Gryffindor great.
Well, it could be that the fanfiction writer is trying to subvert the traditional narrative. Harry has always been the hero of Gryffindor, but in this new take, he hates it. Maybe he sees the flaws in Gryffindor that are often overlooked in the original story, like the over - emphasis on courage which can sometimes lead to recklessness and he doesn't like being part of a house with such a one - dimensional view of what's important.
Maybe he just doesn't like how some fanfictions distort his real experiences in Gryffindor. He might feel that they don't accurately represent his relationships with his housemates or the true nature of the Gryffindor house.
Maybe he hates it because it often distorts the real story or characters he knows. Fanfics can take the story in wild directions that don't align with his own experiences.
Maybe in that fanfic, Harry has had some really bad experiences with magic that made him hate it. For example, he could have seen magic being misused to harm innocent people. Or perhaps he's tired of the chaos and danger that magic always seems to bring into his life in the fanfic.
Maybe in that fanfic, Lupin did something that Harry considered a betrayal. For example, he might have made a decision that put Harry or his friends in danger without consulting them first.
One reason could be that the fanfic distorts the characters he knows well from Gryffindor. For instance, if it changes the personalities of his friends in Gryffindor in a way that doesn't seem right to him.
One reason could be that he doesn't like the spotlight that comes with being a Gryffindor. In the original story, Gryffindors are often in the limelight, and in fanfiction, he might be tired of all the attention.
In some fanfics, Harry might hate Dumbledore because he feels Dumbledore has been using him all along as a tool to defeat Voldemort. Dumbledore has been making decisions for Harry without fully considering Harry's feelings and desires. For example, he didn't tell Harry about the prophecy until it was almost too late, and Harry might see this as a form of manipulation.
It could be that in the fanfic's plot, McGonagall has some past connection to Harry's enemies. So, her hatred towards Harry is a result of her loyalty to those she has a history with. This would create a lot of drama and conflict within the fanfic's story.