A better question I feel is ... where do religious people get their immorality? Greed, intolerance, war?
As far as I'm concerned, "God's Will" is simply the collection of physical, chemical and biological laws that govern the universe, and it is impossible to disobey these laws, as you would expect for such an amazing universe. (It seems silly that God would make so many mistakes and accidentally allow "disobedience" to be introduced into His creation.)
One of the most important biological laws is that of animal survival instinct (or egotism), and we are all subservient to it. Everything we do is an attempt to survive (although because of the complexities of the human mind, and chemical imbalances and regressive upbringings and whatnot, sometimes those attempts are riddled with stupidity.)
The trait of altruism -- helping others -- is subsidiary to egotism. Just like a mother helps her young, and pack animals help their leaders, humans help each other and get that warm "I've just helped someone" feeling, which is actually chemically rigged up.
Likewise, the opposite is also true, in that if we don't obey altruism, we feel guilt, a chemically rigged up trait that warns us that we are doing a disservice to human survival.
However, if we kill someone who is much weaker than us (speaking in more ancient tribal terms), this is a "moral grey area" because survival of the fittest and altruism clash. Does the guilt of killing someone outweigh the understood benefit of eradicating their impediment? Different chemical balances in different people will decide.
Another is the belief in a higher power (or need to explain unknown things), which results from the survival instinct and fear of the unknown, i.e. of death, and is a trait characteristic to human civilisations all across the world and throughout history.
However, the most controversial I would say is the third biological trait -- evolution -- which in my mind will probably eventually phase out the "spiritual" trait because of the ridiculous amounts of death and destruction religiousness causes for human society, and few if any major benefits. Atheist societies will probably survive in the long run.
The notion that morality is something peculiar to humans and its equivalence with the belief in a higher power are, in my mind, flawed. But as a fellow human being, I understand why people feel they aren't
