There is never a reason to be moral, not even with belief in a moral God. One can only be motivated by conscience and the holy spirit.
That's what always seems weird to me about arguments like the one in this article. The only "rational" reason to behave morally is fear of punishment. A believer may choose to behave morally out of love of God, or guilt, or other impulses, but those aren't rational. (Which is not to say they're bad.) In terms of the rational weighing of pros and cons, the only motive is avoiding punishment. So it always sounds to me like the writer is admitting that they only reason they behave morally is so that God doesn't punish them, which doesn't strike me as a very deep moral sense at all.