You're right that theists always claim that without their supernatural objective morality we have none; but they are quite wrong. In fact, I go further and say an imposed set of rules is not a morality at all; being good is not at all the same as being obedient! I also agree with Joan that atheism doesn't demand anything, but it does free one up to have these discussions, and once freed from dogma, we should spot the obligation to pursue a more moral path. We can define a fundamental moral objective and create our ethics that promote this objective. And Bentham / John Stuart Mill did this for us with Utilitarianism. I claim that the extension of this into politics suggests a very liberal / socialist agenda. The challenge is all the dogma that clutters these discussions. Even the most basic assumptions around the ownership of property, the retention of earnings, parental rights etc, are all dogma without fundamental justification. Utilitarianism does not pre-emptively deny these as outcomes, but denies them as inputs to the analysis. This is a main subject of "Age of Wisdumb" - how to see through dogma to find morality and justice. A bit of shameless self-promotion there!