Morality is a big subject in the world of Atheism v religion. On one side we have the religious saying that without god and celestial rules, Rules which, Should they be broken, Are punishable by eternal suffering there would be no morality. And on the other side we have Atheists saying morality is nothing more than a name given to productive social behaviour, A result of empathy and genetics.
We could sit down and explain to the religious how "morality" can come about via an evolutionary process, But going on the luck we have had trying to explain evolution to them it would be a futile waste of time.
Instead what i want to do is explain how "morality" can only, By definition, Exist in someone who doesn't believe in a god.
In most, If not all religions, There is a reward/punishment system at it's very core. Religion comes along, lays down some rules and convinces you that should you break any of these rules you will be subject to torturous punishment, pain and suffering for eternity. For eternity!.
In light of that, How can any action performed by a religious person be considered moral? How can it even be a result of free will? If you are told to do something and threatened with eternal suffering should you not comply or promised a reward should you abide how can your action be considered good? In reality we would call this type of thing at best coercion or bribery, At worst we call it threatening with violence.
The Atheist on the other hand has no fear of a punishment from god and no expectations of a reward. Every action performed by an Atheist is done entirely in the absence of a belief in god and in the absence of the belief that a posthumous reward/punishment system is in place. The Atheist does good entirely because [s]he wants to. Because it's the "right" thing to do.
So next time you hear a religious person claim we need a god to know what is moral tell them that if they need a god to be moral they are in fact the exact opposite of moral and are simply afraid of a punishment and looking for personal gain as a reward for their behaviour. Then ask them if in the case where the nonexistence of god was proven would they instantly start killing, stealing and raping.