We may answer by talking about the evolutionary origins and benefits of things such as empathy.
But it raises a question - if there *is* a god, from where do people get their morality?
Any theist will tell you that they get their morality from the god in which they happen to believe. It is he (it's always a he these days) who decides what is right, what is wrong, and it's up to us to follow that. Seems reasonable. Well, no, it doesn't. But it does seem straight forward.
However there is an issue. Without an inherent ability to tell right from wrong, or at least allocate right and wrong, how does one decide that the morality dictated to them by a god is, in fact, good? If a person has no ability to know right from wrong, without being told, then it's impossible for them to know that the morality they're following is 'good'. They become automatons, unthinkingly doing what is dictated, making no decision themselves, making no judgement calls, or moral decisions.
The problem with this kind of mindless obedience is that it can lead to thinking like this:
@MitchBenn I would absolutely kill babies and women if it was ordered directly by God. God is the only person who can Morally take life
— Andrew P (@Fake_Andrew) August 21, 2015
One can only hope that Andrew P either 1: Is joking (as tasteless as it might be) or 2: Never hears 'voices' in his head telling him to kill. I will speculate here and suggest that if I spoke to Andrew about his declaration that he would murder on behalf of his god, he would say that he *knows* his god is good and *knows* that his god would never get him to do anything that's morally questionable. In such a situation, wouldn't it be better that Andrew's morality was based more on empathy, understanding, discussion, and logic, rather than voices in his head?
Continuing with the speculation, I would question as to how Andrew knows his god is good. Having looked at a few more of Andrew's tweets, I think he'd say that the god in which he believes can't lie and he knows this because the god in which he believes has told him that he, god, cannot lie.
Hopefully you already see the problem. A god who *can* lie, if such god were to exist, could say anything - including that it cannot lie. The statement 'I cannot lie' cannot be believed on its own.
It will be argued here that it's not just that the god in question has said that it cannot lie, but it is the very nature of this god that it cannot lie (that a being outside of nature has a nature is somewhat paradoxical). The obvious question that follows is: Who has defined this nature of 'god'?
If it was the god itself, then we've still no reason to believe it. Any god capable of lying is capable of denying its ability to lie. If it is the believer that has defined this characteristic then the entire premise falls apart. 'I believe in a God who cannot lie, therefore the God in which I believe cannot lie' is pure nonsense and would be immediately recognised as such by anyone with entry level logic skills. They have simply defined into 'existence' a god that fits their preconceived ideas of what a god ought to be.
What does this amount to?
Simply put, someone who believes in a god that gives them their morality has no way of knowing whether or not that morality is good, has no way of knowing whether or not they've been lied to about that morality being good and, at least in some examples, has no justification for *not* murdering people en masse, if they believe their god has commanded them to do so.
I don't see this as the kind of morality that should be trumpeting itself as superior.