Where do atheists get their morality from?

[discordianpope]

I'm arguing from a purely philosophical position, one where objective moral values don't exist. This is the default position of atheism from which our moral norms are derived. The problem is, our atheistic position cannot RATIONALLY reject the possibility of genocide, rape, murder and the likes being morally good. There is always the possibility. And more importantly, it's a metaphysical possibility, not just a logical one.

This is worrying for the rational atheists among us, and this is an area I am enormously interested in researching. My problem is, I need a better grasp of the fundamentals of ethics and moral studies.

I don't buy this. But even if true, is a theist really in any better a position. I mean, if morality is based on God's will and God can will that genocide is moral, then well I guess a theist would just have to accept that. It's just the euthyphro dilemma. Either there are true moral propositions which exist independantly from God or God can make rape moral. This kind of theistic morality is as shifting and unsure as any secular morality.