While Volemort is much like Hitler/Angel of Death, Bellatrix is the Commandant. If your anything but Pureblood, your a threat to the very existence. While families like Malfoys, Potters, Weasleys, and Black family for example were pureblood, they didn't start as one, but became pureblood overtime. Bellatrix did her bit as a commandant, while some of the other death eaters chose sides. "Your either with us, or against us." Thankfully, no camp was mentioned, but many kids must have been home schooled as young witches or wizards came of age with blood status in question.
