free love
Well, that's Berg's unique revelation: God is changing the rules, and his prophet David was sent to pour out the "new wine" that God's servants are free to have sex with whoever and whenever. Zerbster was the wine-taster, and if it didn't hurt her, it won't hurt you--unless, of course, you are weak in your faith, demon oppressed, or otherwise unfit to drink the new wine.

The "new wine" of free sex didn't hurt Zerbster and many like her because they lack a capacity for empathy and compassion. It mortally wounded Ricky (and people like him) because he was an extremely empathic person by nature.