Mugglenet isn't even close to the majority of harry potter fanatics, they are the hardcore of the hardcore of the hardcore crowd. There was something similar for the Fallout franchise called No Mutants Allowed, and pretty much every one of them called Fallout 3 a disgrace to the franchise and threw ever bad word at it you could think of. When Fallout 3 broke records for the franchise, they still hated it with a passion for not being a "true" fallout game.
Mugglenet is No Mutants Allows for Harry Potter, and can be safely ignored as being too extreme to the franchise. When the creator of the franchise signs off on something, but these rapid fans don't like it, you can pretty safely assume they'll hate anything new.