The most common attempts to discredit atheists in discussion stem from misrepresentation. If only Christian apologists could understand their opponents’ positions, they would have a chance at discrediting at least some of them.
Of course, preachers and apologists aren’t exactly talking to a critically-minded crowd most of the time: they’re preaching to people who already believe them or are in desperate enough situations to be willing to believe anything, and thus, don’t really have to face much criticism for their straw-man attacks on atheists. This is why the same criticisms of atheists come up again, and again, and again when Christians and other theists try to discredit nonbelievers.
Atheists “Don’t Believe in Anything?”
This statement is ridiculously common: “Atheists don’t believe in anything.” Sorry, theists, but that’s far from true – very few atheists are nihilists. Atheists just don’t agree with you. Assuming that disagreeing with you equates to nihilism merely shows that you theists tend to be rather closed-minded, and unaware of what other metaphysical and philosophical positions the world has to offer.
“Atheists don’t believe in a higher power than themselves,” is another way theists often word their irrelevant attack. Sure, atheists believe in powers greater than themselves almost all the time, it’s just that those “greater powers” tend not to be comfortable, familiar mirror images of themselves.
Atheists (especially scientifically-minded ones) believe in the great powers of things like genetics, gravity, logic, and black holes, while theists believe in a “greater” mind which, while more awesome than a human’s, is intuitively familiar and easy for even a child to understand. What power is really greater than us – the blind causal forces that only humanity’s best minds can wrap around, or a giant supernatural “person” who thinks and behaves like a jealous, sadistic, violent thug?
Atheists “are Angry at God?”
This one is downright insulting, but if the atheist can stay calm in the face of it, she can see right through it: it’s merely a circular argument. The theist who explains atheism by saying that atheists “are just angry,” can’t even accept that some people actually are atheists. This is merely a denial that atheists exist, which is silly: there are millions of atheists, many of whom are members of non-theistic religions, and don’t even know anything about the Christian/Muslim/Jewish god. The rest know about the Western god and say, “Nah, I don’t think that’s true. I’m not desperate enough to be convinced of something so ludicrous.”
To say to an atheist, “You’re not an atheist,” is a laughably transparent attempt at flat-out denial.
Yet, it is true that some people begin to move toward atheism due to initial anger at god. A Christian may realize that a just god would not have allowed his brother to die in a car crash, or his house to burn down due to arson, or just can’t accept that a loving god would allow millions of children to die in poor countries of disease and malnourishment each year. Being “angry at god” is often the first step in the process of realizing that the Christian religion, and even theism in general, doesn’t make any sense.
But someone who is angry at god is not an atheist – if you’re angry at someone, you must think he exists. Someone angry at god might become an atheist soon, though – hopefully!
Atheists “Have no Morals?”
Theists like to assume that their morals come directly from their god, a being open to interpretation, which they’ve never met or even seen. Atheists, on the other hand, usually claim that morality comes not from some outside force which imposes morality on us “sinful” humans, but from the compassion and reason innate and nourishable in all human beings.
Atheists have morals (almost all the time) – and usually, the atheist’s understanding of morality is more abstract, complex, and subtle than the theist’s. Atheists usually hold that the best way for us humans to find morality is by searching ourselves and our surroundings, rather than an ancient text full of genocide, rape, slavery, sexism, and abuse.
Because religious people rarely, at least in North America, tend to stone teenagers for being disobedient or force their daughters to marry their rapists, it can easily be argued that theists don’t get their morality from their holy books (at least when their quality of life is high) – they get it instead from the same place everyone else does: their peer group, their reason, and their compassion.
The Myth of “True” Atheism (Atheism as a Religion)
Sometimes, atheism is discussed as though it’s some kind of club or even a religion. “True” atheists are said to “believe there is no god,” while one who says, “I don’t believe there is a god,” is said to count only as an agnostic – not a “true” atheist.
This is a skewed view. Atheism is not a group of people with a leader, and it doesn’t branch off into sects who tell one another who counts as a “true” adherent. That’s what Abrahamic religions do, not what atheists do – atheism isn’t about picking a herd to join, it’s just a philosophical position about god(s).
Atheists tend to chuckle knowingly at the notion that trying to rally with their fellows can be a lot like ‘herding cats:’ most atheists go their own way, and just happen to have one thing in common: they don’t buy into the ‘god’ notion.
All it takes to be an atheist is to hold a position lacking belief in god, whether this is stated in a positive or negative way. The difference between the positions is subtle, but both positions count as atheism. There are several kinds of non-belief in god.
Agnosticism
While not a negative position on the existence of god, agnosticism is a negative position on belief in god. Agnostics generally say, “There is no good evidence for god, so I have no reason to believe. But I don’t know that there’s no god, either.” Agnostics sit on the fence about god because they haven’t been shown good reasons to believe.
Soft Atheism (aka, Nontheism)
Second on the list, as we travel the soft-to-hard road, soft atheism is very similar to, and sometimes even indistinguishable from, agnosticism. The difference is primarily philosophical: while agnostics say that having no evidence, either way, permits agnosticism, atheists say that having no evidence, either way, permits atheism. Daniel Dennett, a philosopher of mind and professor at Tufts University, is a good example of a slightly soft atheist. Soft atheists tend to be pretty mellow about their position. 
Agnostics take the position that when evidence lacks, one should stay neutral. Atheists find that when propositions lack supporting evidence, one should instead take a negative stance. Realistically, we lack evidence for an infinite number of possible propositions. Some propositions don’t even make any sense. Just because we have no evidence, should we say, “Maybe that proposition is true”? More importantly, should we behave as though nonsensical or unlikely propositions might be true? Atheists say “no,” while agnostics either say “yes,” or “I’m not sure.”
Militant Atheism (aka, Antitheism)
Militant atheists have found that there is no reason to believe in any gods, and that because it is so unlikely that gods exist, people should behave as though they don’t – that is, at least, unless some good contradictory evidence comes in. Atheists have, generally, come to be very sure (but not completely – maybe 90 to 99% sure) that there are no gods. They’re technology agnostic, but sure enough about it to call themselves atheists. This is the atheistic part of a militant atheist.
The militant atheist lacks passivity about theism in society. Militant atheists care that others believe in god; while they rarely, if ever, try to “force” disbelief on others, they would prefer it very much if others abandoned their belief in god, or at least refrained from pushing it on others and demanding “respect” for their beliefs.
This antitheism stems from the observation that theistic religion can do significant damage in society, from supporting tyranny to frightening children, and meddling with proper science education, thus affecting technology, medicine, and a population’s general quality of life. Richard Dawkins and Sam Harris are good examples of anti-theists.
Hard Atheism
Hard atheists are often, but not always, antitheists. Penn, of the Penn and Teller stage-illusion duo, is a self-proclaimed hard atheist: he actively believes there is no god: that means he’s 100% sure that no god exists. Many prominent philosophers claim that this is an indefensible position – it’s not really possible to prove that something is one hundred percent untrue, especially something deliberately constructed to be unfalsifiable, like the Abrahamic deity.
It’s easy to nitpick about exactly what counts as atheism, and which position counts as atheistic, agnostic, militant or passive. While religious people pick a demonation’s umbrella to fit themselves under and adhere to, non-theists, agnostics and the like are free thinkers, chased by umbrellas, and labeled after they’ve taken their stance, rather than before.
This means there are probably about as many kinds of skeptical approaches to theism as there are skeptics. The best way to learn about any given atheist’s position is to avoid pigeonholing – and just ask!
