'why behave with any moral scruples?'
Why indeed? Perhaps and this is only my opinion from a social science perspective, society stamped down of murders, rapes, etc with moral codes, which admittedly differ from country to country, we all evolved different cultures; but do we not live by a moral code because of societal pressures?
Certainly I do not believe if you discount an after life you will become a mass murderer or rapist,
Skepticism is the agent of reason against organized irrationalism - and is therefore one of the keys to human social and civic decency.
Stephen J Gould MY BLOG PAGE