It could go either way. If the fanfic shows Harry in a really positive light, like a super - powerful wizard who is also kind - hearted despite their treatment of him, they might feel a bit guilty. But if the fanfic portrays Harry in a negative way, they might feel justified in their own cruel behavior towards him.
Well, it's hard to say exactly. Maybe Mr. Dursley would be outraged at how his family is being fictionalized in these fan - created stories. He's so proper and hates anything out of the ordinary. Mrs. Dursley might be more interested in how people are writing about her cooking or how she runs the household in these fanfic versions. Dudley, on the other hand, might just be confused as to why anyone would write stories about his family at all.
They would likely be disgusted. The Dursleys are so anti - magic that any form of fan - created stories about the magical world would be abhorrent to them.
The Dursleys' reaction would be complex. Vernon would be enraged and might even try to burn any fanfiction he found. Petunia would be conflicted. Part of her would be disgusted, but a small part might be a bit curious as she has some connection to the wizarding world through Lily. Dudley might be more interested than his parents, especially if the fanfiction had some action or adventure that appealed to his more adventurous side.
Their view might expand. They'd see different takes on the wizarding world that they hadn't considered before.
They'd probably be horrified. The Dursleys are very much against the idea of magic, and fanfiction might introduce even wilder ideas about the wizarding world.
It would completely shatter the positive perception of Harry. He is known for his kindness and ability to forgive. Such an act would make him seem like a cold - blooded killer, which is the opposite of how he is in the original series.
His decision to leave the Dursleys can make the plot deviate in many ways. In fanfic, it could mean that he doesn't have to wait for the official Hogwarts invitation. He might seek out the wizarding world on his own. This could lead to him encountering different characters or facing different challenges earlier. Also, his departure might make the Dursleys more or less relevant in the overall story. If they are no longer a factor, then new antagonists or plot elements need to be introduced to keep the story interesting.
They are often portrayed as the villains. Their years of treating Harry badly are brought to light. They might look scared and out of place in the wizarding courtroom, with all its strange sights and magic.
Their view could become more confused. Fanfiction can present all sorts of alternate universes and character developments. The Death Eaters, used to a very specific view of the wizarding world under Voldemort, would find it hard to accept different versions. They might see the wizarding world in fanfiction as a chaotic and wrong place, which would make them double down on their own views to feel more secure.
The story could take a darker turn if he refuses to go back to the Dursleys. Maybe without the protection of the blood magic at the Dursleys' place (even if they were cruel), he becomes more vulnerable to Voldemort's attacks earlier. Or, on the other hand, he could find a new form of protection that was not part of the original story, which could change the power dynamics in the fight against Voldemort.