Why 'should' atheists be moral?

[mralstoner]

It has been said that as an atheist the meaning of your life is basically to maximise the amount of pleasure and minimise the amount of pain in it.

This is a caricature of most atheists I know, and it is shopped around by theists wishing to portray atheists as thoughtless hedonists who are inherently selfish.

A foundation of emotional values does not necessarily equate with "hedonism". All humans are motivated by emotional fulfillment, it's an inescapable biological fact that all human action is motivated (in terms of end goals) by emotional rewards. We just do it in different ways, whether atheist or religious, liberal or conservative, stoic or impulsive, etc.

All humans work to "maximise pleasure and minimise pain", but we don't all have the same beliefs about how to go about that.