Board Thread:Wiki Discussion/@comment-25958552-20160731111602/@comment-32182236-20171224200551

They probably think that because it fits the "spirit" of the game-If every other character's actually good, they figured Chara being evil breaks the spirit of the game. Yeah. That's their main reason. Even though Asriel flat-out says there's Floweys out there, and not everything can be resolved by just being nice, a clear contrast to that. The message of Undertale is not "everybody's just a misunderstood great person." Asriel, the most pacifistic of the bunch (Except maybe Pacifist Frisk), even HE says there exist those who truly are evil.. He says this about the Surface world..

Yep. That seems to be their common motif... Even though that's not backed by canonical evidence. They do use evidence to defend some problems with said theory, though... But considering my counterargument, they might just figure it out..