The only possible basis for a sound morality is mutual tolerance and respect: tolerance of one another’s customs and opinions; respect for one another’s rights and feelings; awareness of one another’s needs.
If 'god' is a metaphysical term, then it cannot be even probable that a god exists. For to say that 'God exists' is to make a metaphysical utterance which cannot be either true or false. And by the same criterion, no sentence which purports to describe the nature of a transcendent god can possess any literal significance.
If the assertion that there is a god is nonsensical, then the atheist's assertion that there is no god is equally nonsensical, since it is only a significant proposition that can be significantly contradicted.