Because you're scary.
Stephen: You said you ain't know him.
Stephen: I said, "You said you ain't know him."
Broomhilda: I don't. Stephen: Yes, you do.
Broomhilda: Mister Stephen, I don't.
Stephen: Why is you lying to me?
Broomhilda: [on the verge of tears] I ain't.
Stephen: Then why is you cryin'?
Broomhilda: You scaring me.
Stephen: Why is I'm scarin' you?
Broomhilda: Because you're scary.