My impression is that most people who see any inherently- evil species in a fantasy work as a nasty sign of conscious or subconscious racism gave up on Buffy as soon as it started, but that among people who watched Buffy at length the opinion is chiefly found in the kind of Spuffy shippers who have been yelling their hate for Buffy ever since it began to be clear around mid-S6 that ME did not share their reading of the characters.