Kind of standard moral moment. It's wrong to kill monsters if there are child monsters involved.
It always feels weird when people (as in authors and readers) treat these half-human half-beast races as having all traits of the animal except body shape and intelligence. It's like they forget the half-human part. Although by the way she says it, they're vegetarians by culture (and not universally at that), not herbivores by nature, which makes more sense to me.