This is a wedge that the religious like to drive between two positions that, typically, have more in common than they want people to think. After all, if you think atheists believe they can be absolutely certain there is no God, then there are almost no atheists in the world, and Richard Dawkins would, on that definition, be an agnostic. Here, for instance, is what Dawkins wrote on HuffPo two years ago:
The slogan on the buses will read: “There’s probably no God. Now stop worrying and enjoy your life.”
This appears to be a tactful retreat from Professor Dawkins' previous claims that God "almost certainly" does not exist - but commentators are already pointing out that it is closer to agnosticism (uncertainty about whether God can be known as a reality or not) rather than atheism (outright denial).
Accepting, then, that the God Hypothesis is a proper scientific hypothesis whose truth or falsehood is hidden from us only by lack of evidence, what should be our best estimate of the probability that God exists, given the evidence now available? Pretty low I think, and here's why. [...]That sounds, to me, entirely compatible with what the Atheist Bus Campaign is proposing to put on buses. The difference is one of degrees, between "probably" and "almost certainly", both phrases which acknowledge uncertainty. I would argue that the Atheist Bus Campaign chose the wording it did mostly because it was trying to be pithy, not because they wanted to water down the atheist position. They are, after all, calling themselves the Atheist Bus Campaign.
Similarly, Bill Maher recently went on the Daily Show to promote his new film Religulous, which is, to all intents and purposes, advancing atheist arguments. Nonetheless, Maher claims for himself not atheism, but agnosticism. Now, an agnostic is "someone who does not know, or believes that it is impossible to know, whether a god exists". If that is the case, then why argue, as Maher (correctly) does, that the beliefs of religious people are preposterous? If you're agnostic, you are allowing that there is a reasonable case to be made both for and against the existence of a particular God, or at least that there is no robust case to be made against their existence. So why try?
I think the problem here comes from the wide range of definitions claimed for atheism in common parlance. Atheism can be "either the affirmation of the nonexistence of gods, or the rejection of theism. It is also defined more broadly as an absence of belief in deities, or nontheism." Thing is, most atheists aren't "affirming the nonexistence of gods", they are "rejecting theism". Religious apologists want you to believe that I believe there is definitely no God. I don't. I just think the claims of religions are bonkers, and as such the burden of proof is on them, not me. But don't call me agnostic. The only uncertainty I have is the technical kind of uncertainty that I also hold about the Flying Spaghetti Monster and Russell's Teapot, both equally bonkers propositions.