Ans.01. Don't project your theist loathing and nihilism on atheists. Just because you can't imagine a life outside your God's a-hole doesn't mean nobody else can.
02. If you can't imagine a good moral life without a belief in an imaginary being than by all means DO NOT LEAVE YOUR FU&KING CHURCH. Without your religion you would run amok killing and raping? Is that what you're saying?
01. If atheists have no belief in any God or any Divine Guidance, what is the basis of their "morality"?
Their Morality is as shifty as their own beliefs. On day they might consider one act as "Moral" and next they might declare it "Non Moral" and Vice Versa.
Look at the case with Sodomy and Lesbianism?
Atheists of 100 years back termed them as "Immoral" but the same has become "Moral" for our present day Atheists.
I want to ask you, from a purely Atheist point of view, why should you not rob?