Dumbledore bashing, for better or worse, has completely reshaped the landscape of Harry Potter fanfiction. It's the foundation for a whole subgenre of fics that are fundamentally about subverting the original narrative's authority. By portraying Dumbledore as manipulative, greedy, or outright villainous, authors can instantly create a world where the established order is corrupt and Harry (or another protagonist) is justified in breaking every rule and forging a completely different path. This provides an easy engine for power fantasies, political intrigue stories, and darker 'Harry raised by someone else' plots.
But I think the real impact is more subtle. It's changed how readers engage with canon. It forces a re-examination of Dumbledore's actual decisions—the questionable placement of the Mirror of Erised, the lack of protection for Harry at the Dursleys, the whole 'raising him like a pig for slaughter' line—and amplifies their negative potential. This lens can be incredibly liberating for writers; it throws open the doors for Slytherin!Harry, Independent!Harry, or Harmony pairings because the main moral authority figure is removed. The downside is it can lead to lazy writing where Dumbledore is a one-dimensional cartoon villain just to make the protagonist look good, stripping away the tragic complexity Rowling wrote. Still, you can't deny its influence; it's a dominant trope because it works so effectively to set a new story in motion.