By ‘atheism’, I mean what is commonly referred to as ‘strong atheism’. Strong atheism is the position that gods do not exist. Specifically, strong atheism can also be local. In other words, classical strong atheism is the denial of classical/traditional theism. And classical/traditional theism is the position that there exists a God who is all-powerful, all-knowing, and all-good. Therefore, ‘classical atheism’ denies that such a God exists.
One might think that the negation of theism (~T) does not by itself generate predictions about reality. That might be true to an extent, but atheism is a disjunction of positions. For example, metaphysical naturalism is one form of atheism, so naturalism entails that God does not exist (~T). And clearly, metaphysical naturalism does generate predictions about reality. Therefore, one can generate predictions from specific forms of atheism, and specific forms of atheism are atheism (even though atheism itself isn’t identical to it’s specific forms, like naturalism)
To be clear, not all atheists are strong atheists. And, not all atheists are naturalists. But naturalism is atheism, even though atheism isn’t necessarily naturalism. However, many atheists are naturalists, and many atheists do have a world view.
Also, when I compare something like naturalism to theism, I’m not even saying that naturalism is true. Like all world views and metaphysical views, I’m skeptical of naturalism to some degree. Rather, I bring in naturalism to show how certain world views perform poorly, given the data. Thus, I’m utilizing naturalism as a hypothesis to show that certain world views are certainly false, very probably false, or probably false. However, I will say that I find metaphysical naturalism to be plausible.
Thus, when someone says something like, “evil is not surprising on the no-God hypothesis”, they might very well mean something like, “evil isn’t surprising on the hypothesis that natural things are the only thing that exist” or “evil isn’t surprising on the hypothesis that there aren’t any supernatural beings that are good.” Heck, one could argue that evil is more expected on deism or pantheism than on classical theism.
Not to mention, when one is arguing that evil is evidence against God, they are obviously including things like “the universe exists” in our background knowledge.