Of course it's amoral, when you think about it. That doesn't mean that individual atheist is amoral. But he or she is moral for reason outside of atheism, not because of atheism.
Atheism is amoral because it's a worldview that everything including life came from nothing, by chance, and that it will all ultimately end in nothing.
So it's nothingness at the beggining and end, and in between is chance. That's the highest principle that sets up atheistic existence.
It's obvious that there's no place for true morality within atheism.
But there is place for hedonism. What seems like morality withinin atheism is just a form of hedonism.
It's "whatever rocks my boat" attitude. There can't be morally good or bad if existence is set up by chance, from nothingness, going into nothingness. But there can be pleasure.
In atheistic worldview, one person can think that peace is good and war is bad. But that's just his or her private hedonism. Other person can think that murder is great, and that's equally fine, since everything came from nothing, is governed by chance, and ultimately goes back into nothing. Both opinions are perfectly in line with foundation of atheistic existence.
So, if hundred people group together and make a weapon that ends up killing everybody on earth, that's neither good or bad within atheistic worldview. That was just an event that was ultimately governed by chance.
Yes, that event is subjectively bad for murdered people who can't exercise their hedonism anymore, but that principle - to exercise own hedonism - is far, far below principles of coming from and ending in nothingness, by chance. Probably even infinitely below those foundational principles.
