Because the sheep were taught to ignore the differences between a sheepdog and a wolf. After all, they're the same species, right? (ie, "There's only one race, the Canid race!!")

EDIT: Speaking of which, look at the nazis worried about preserving the purity of the wolf race from dirty mutts: https://phys.org/news/2021-07-method-unambiguous-identification-wolf-hybrids.html