How we cite our quotes: (Act.Scene.Line)
Quote #1
And the child-bride in her nightie
Whose assailant's still at large
Violated in her slumbers—
Mackie, how much did you charge? (P.39-42)
The opening number, "Mac the Knife," recounts Mac's various crimes. While most of them involve murder and theft, this one reflects his fatal flaw: his lust. The "violation" refers to rape, a horrible crime, which foreshadows Mac's lustful habit of seducing women with trickery.
Quote #2
MRS. PEACHUM. A fine opinion of your daughter you have.
PEACHUM. The worst. The very worst. A lump of sensuality, that's what she is. (1.1.177-179)
When Polly gets married behind her parents' backs, they judge her harshly. From being their daughter, she has transformed into a sexual being which, in the eyes of the Peachums, is "the worst" that could happen. Rather than a human being she's now a "lump"—not exactly flattering.
Quote #3
MATTHEW. And besides, I never use filthy language with her. I respect Kitty too much. But maybe you wouldn't understand that, the way you are. You're a fine one to talk about filth. Do you think Lucy didn't tell me the things you've told her? Compared to that, I'm driven snow. (1.2.146-150)
Mac calls Matthew's girl, Kitty, a "slut," which offends his buddy. He claims to respect her, unlike Mac's attitude toward his women (yes, plural). Matthew understands that language reflects respect or disrespect, while Mac either doesn't understand it, or just disrespects everyone he lusts after.