Ah, right.... [She figures Ririchiyo deserves an explanation for why they're treated that way, since there is one important reason.]

You guys don't - eat magic, right? That's why those kinds of offspring are killed. They have all the strengths of a Witch and a Demon, but in order to survive they have to feed off our magic. When they get exiled they're sent to human regions, where they starve to death since humans have no inherent magic they can eat.