I recently came across a post on Think Atheist that I thought very neatly summed up the lack of any logical necessity for god in moral philosophy amongst sane, mature individuals. The post on Think Atheist was so good it deserves to be repeated:
"If something is moral because God wills it, why does God will it?
Does he have a reason? If he has a reason, then the moral exists independent of God.
If he has no reason, then the moral exists at the whim of God and is totally arbitrary. "Thou shalt not kill" could just as easily have been, "Thou shalt not cover your bodies", or "Thou shalt not eat after sundown".
Logically, theistic morality can ONLY be arbitrary and spurious. True morality has its reasons -- independent of God."
And therefore true morality exists independent of god. What role is then left for god? Only the threat of punishment--for those who appear to be unable to use empathy and reason and respond only to a threat (i.e., small children and psychopaths). As I mentioned before, most religious people claim to be such people.
Someone else posted a similar inquiry on Yahoo Answers 4 years ago and received an insightful response that echos some of my own thinking:
"Because if morality "comes from god", then anyone who does not belong to that religion is immoral, or a criminal, or is someone deserving of a concentration camp.
Faith is how you treat "god". Morality is how you treat people.
Theists don't want to admit this because it means they can't rationalize or legalize their hate and violence."