How can one rebut the argument that atheism is inherently immoral?

Question

It not uncommon to see religious people arguing that without the moral center of a religious text, true ethics are impossible. The reasoning goes that, without a fixed moral center, atheists are free to make up their own beliefs about what is right or wrong. And while the majority of them make the "right" choices, roughly in line with "objective" religious morality, nothing forces them to do so. They could, for instance, adhere to the ethical arguments about stealing being the correct and moral thing to do in cases of extreme inequality. Or, in a more extreme case, justify killing other humans on the basis of their actions or beliefs. Instinctively, this argument feels wrong to me. After all, if it's really that simple, why do so many atheists make the "right" moral choices? And why do some religious people go to great lengths to justify stealing from or killing those of other religions. Yet I cannot formulate this argument into sensible propositions. Is there a good rebuttal?

Answer 1

I do think that, if you find a religious text authoritative, it would be easier in some cases to "determine" what one should or shouldn't do. If you're wondering whether it's wrong to do X, and you think religious text T has an answer and that it's the right answer, then all you have to do is to see what T has to say about it.

However, just because it's true that, in some cases, it's easier to get what you'd think is the right answer about a moral question if you have a text that you think has the right answer, it doesn't follow that "without the moral center of a religious text, true ethics [is] impossible." It seems to me that Aristotle did some really good ethics, but none of his ethical principles are derived from a religious text that he found authoritative. (He did talk about "the gods" as if he believed in them, and he does argue for a prime-mover of the universe, and so in some sense I think it would be a mistake to think of Aristotle as an out-right atheist. But this does not affect my point: regardless of Aristotle's religious leanings, his ethical thought is both powerful and plausible, and his ethical thought does not rely on any religious text that he takes to be authoritative.)