[voice]
Muggleborn is what prissy girls say. They're actually called mudbloods.
Muggle parents are horrid. Some of them beat their children for doing accidental magic, and you don't know which ones, so it's best not to talk to any of them until you're old enough to stand up for yourself and curse them if you need to.
He's right...and don't just call him 'Lucius,' that's awfully disrespectful.