People that say "What keeps atheists from raping, murdering, and stealing if they don't believe in God?" want to rape, murder, and steal from you but they're worried God will catch them.

Whenever anyone uses this as proof that atheists are untrustworthy or bad people, they're actually strongly suggesting that they themselves are bad people.

Turn it around and ask them - "is the only reason you're not doing those things is fear that God will punish you?"