Mark Kennedy, the police officer who infiltrated environmental protection groups, has said he is sorry for betraying his friends.
Why do people feel sorry when they do wrong? Bertrand Russell thought morality came from peer pressure. Being an atheist, he was of course completely wrong. That was precisely how Nazi Germany started. Let's just keep that Nazi/atheist association firmly in our minds.
No, feelings of right and wrong seem to be part of our very being. Martin Luther, someone who had only just recently stopped being a Catholic and so has a chance of being occasionally right, put it clearly when he said "I can do no other."
We Catholics have a thing called a "conscience". Ever since Vatican II pointed out that having a conscience was a good thing, we Catholics have been obliged to consult our "conscience" when we find ourselves facing a moral problem. Unlike other religions, we don't automatically think whatever the Pope thinks, or consult our catechism to decide whether abortion, contraception or gayness is wrong. That's why there's such a wide variety of opinion among Catholic bishops on these matters.
When we consult our "conscience", what we're actually doing is consulting the Invisible Magic Friend. We know this because a hymn says so.