There could be some people who have a very warped view of the creative process. They might say 'harry potter is alpha fanfiction' because they see the vast amount of fan - created content around 'Harry Potter' and somehow think that the original work is a form of fanfiction. However, this completely ignores the fact that J.K. Rowling created the entire 'Harry Potter' universe from her own imagination. It could also be that they are influenced by some non - mainstream literary theories that distort the concept of original works and derivative works.
Perhaps someone who has a very different perspective on the definition of literature and fan - created works. They might be trying to make a point about how 'Harry Potter' has elements that they think are similar to what might be found in fanfiction, but they are wrong. It could also be someone who just wants to stir up controversy without really understanding the nature of 'Harry Potter' as an original creation.
One reason could be copyright. The creators and rights holders of Harry Potter want to protect their intellectual property. Fanfiction can sometimes blur the lines of ownership and might use elements of the story in ways that aren't authorized.
Perhaps they don't fully understand the depth of the world - building. They might see all the magic and think it's just some random, crazy ideas thrown together like in a not - so - well - thought - out fanfic.
Perhaps they haven't fully understood the series. Some people might just skim through the books or movies and miss out on the depth. They could be focusing on just the surface elements like the magic spells and not realizing the complex relationships and themes beneath.
Perhaps they've come across some really strange fan - created stories. Some fanfictions can be very out there with their interpretations of the wizarding world.
Maybe they want to emphasize the purity of the original 'Harry Potter' story. They don't want it to be confused with the many fan - made stories out there.
One reason could be that they feel the official Harry Potter story has a defined end, and the fighting in fanfiction is just over - done. They want to focus on the original tale's conclusion.
Maybe they just want to be controversial. Some people like to make extreme and untrue statements to get attention.
Maybe they just don't understand the real essence of Harry Potter. They might have only seen a small part of it or misinterpreted some of the more emotional or character - developing moments as signs of weakness, which is completely wrong.
Maybe because they are a big fan of the original 'Harry Potter' series and are tired of seeing really bad fanfiction. They want to emphasize that the real 'Harry Potter' is much better than those poorly - made versions.
One reason could be that they are a huge fan of the original books and movies and think that fanfic often takes things in the wrong direction. They might feel that the creativity in fanfic goes against what they love about the original Harry Potter, so they reject it completely with that statement.