When people say: “I knew it was wrong, but…”, what they often mean is simply “I know people think it’s wrong” or “I feel it’s wrong but I’m not sure why.” There is no easy remedy for this, since moral uncertainty is a part of the human condition. To do our best might, therefore, simply mean taking morality seriously and really thinking about what we ought to do rather than readily succumbing to our self-serving instincts when dilemmas get too tricky. On this account, we do wrong willingly because we refuse to think too hard about whether what we’re doing is right.
Julian Baggini in FT Magazine, February 2nd, 2013
Morality is elastic and is open to being interpreted in self-serving ways. We invoke morals to pass judgement on the behaviour of other people, but believe in our heart of hearts that our own personal freedom of choice takes precedence over any external moral code. So if we “do wrong” we still somehow feel that we “do right”.