Ginny Weasley looked as though she could spit fire at this lady. That's probably why she was called upon to answer -- and also, well, she's kind of hard to miss with that red hair.
"Ginny Weasley," she stated, not even trying to hide the loathing in her voice. "But you already knew that. Muggles are just like witches and wizards but they don't have magic. It's all right though, because muggles have learned to adapt and live without using magic as a crutch. They develop technologies that are progressive and meanwhile we're stuck on living in the past. You and and many other stupid Purists are afraid of them because you think that they're a threat to us."
She paused for a moment and then said with a smile: "Without muggles, wizardkind would be dead. The inbreeding would have destroyed us. You and your brother would know a little about that, wouldn't you Professor?"