There's two camps.Is it specifically Harry Potter or Rowling certain net denizens are protesting? I thought when they decided to hate something it was a full package but I recently read an article that suggests it's just the author they have a problem with.
One which collectively dropped HP because JK is still getting royalties and refuse to contribute to her through any official productions. That the quality of the product or vibe you get from fandom doesn't matter so much as what supporting the product does feeding a TERFy jerk who uses her fortune to further TERFy jerk agendas.
The other also has that but insists that HP wasnt really a good story anyway and about as thought provoking on the subject as Twilight was about vampires (and about as origonal. With HP not even being the best "British magical school" series.) And also contains a lot of gross things like antisemitic imagery, slavery apologetics, lots of racist stereotyping, etc. Basically that camp is "I beg of you please read more than this. There is better than this."