[She inhales sharply.] Bellatrix. I found out just how much she hates Muggle-borns. [Among other things she didn't know happened because she was upstairs getting tortured til she passed out.]

Maybe he becomes that way when left at home. But I saw him at the manor and I've watched him here. There's something about him. He doesn't want to do any of that. He's not like his father or aunt at all. He doesn't take joy in torturing people.