Because it reflects poorly on the yandere community, and sends the message that doing this stuff is okay because it will make you like those kawaii yandere characters

You're a lolicon, you're familiar with the defense if the more "messed up" fetishes with them being just drawing in fiction, not promoting real acts of depravity

Making this woman awaifu is basically invalidating that because it celebrates a real act of depravity, the drawings are celebrating a real criminal who committed a real act of violence. People who argue that there's something wrong with yandere fans will point to this as concrete evidence to their claim