All We Have
So the upshot of all that is (since the implied question was, if I understand it correctly, how do atheists manage to believe in objective moral standards?) that I do think there are objective moral standards, if ‘objective’ means generally applicable, and generally applicable for sound, articulable, sharable reasons; but I don’t think they’re guaranteed by anything external to humans; I think we have to give reasons for them; and I think they are human artifacts, not something in nature or part of the fabric of the cosmos. That’s sad, in a way. It would be nice if animals had a moral sense, but they don’t. (They have affections, or something like affections, which prompts them to treat some conspecifics well within certain limits, but that’s about it, and that’s a pretty rudimentary version of morality.)
But thinking moral standards are human artifacts doesn’t weaken them. On the contrary. Theists have the option of thinking that god will make things come out all right eventually (or after we die), that wickedness doesn’t, finally, flourish like the green bay tree; atheists don’t have that option, so we know damn well that we have to keep the old moral standards in good repair, because they’re all we have.