"You are trying to make me feel guilty by quoting the Ten Commandments."

Ask the person which one of the Ten Commandments makes him feel guilty. Simply state, "The Bible says, ‘You shall not steal.’ If you feel guilty when you hear that, why do you think that is? Could it be because you are guilty?" God gave us our conscience so we would know when we break His Law; the guilt we feel when we do something wrong tells us that we need to repent. See also Romans 2:15 footnote.