"I can explain that one," said McGonagall, who had been alive and an adult during that war, from the vicinity of the teakettle. "Gellert Grindelwald did not discriminate against Muggleborn witches and wizards the way You-Know-Who did. As far as he was concerned, anyone with magic was part of the superior race." She shook her head, looking a bit sad. "If you could measure the number of Squibs in the world, I think you'd find that they were the ones who were most victimized in that war, especially since unlike Muggleborns, they cannot defend themselves against magic with any effectiveness."