Where do atheists get their morality from?

[Vincenzo Vinny G.]

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.

No, it really isn't.

You wish it wasn't. We all do.

But any argument for objective morality fails without appealing to an objective standard. And seeing as our epistemic limitations cannot provide us an objective standard, but rather a subjective one (considering (a) subjective cognitive limitations and (b) inherently neutral moral authority of all moral agents), we are forced to concede that there is no rational basis for objective morality as an atheist, and in some possible world, without a necessary being, or objective source, it would be morally good to eat babies, or whatever other moral abomination you can think of: wearing white after labor day, for example.

This is the position of pre-eminent atheistic moral philosophers of the past 50 years as far as I can see.

As far as I can see, the easiest way for an atheistic worldview to escape this problem is to attack (b) and say that one human being is morally perfect, and thus everything he says is morally good. But we can't do that.

Or we can attack (a) and say that human beings have perfect cognitions, are omniscient, and therefore make consequentialistically (pertaining to a consequentialist theory of morality) perfect moral decisions. A deontological moral theory would be better covered by the attack on (b) as detailed above.