The number one cliché I hear about atheism is that lacking an objective / transcendent / absolute morality, everything is permitted, and surely we must be eating babies for breakfast. Religious people seem to be very insistent on this point, and all but attempt to push us to be immoral, telling us that we are being inconsistent if we aren’t, and that ours is a self-defeating position.
There are quite a few parts to deconstruct in those assertions. First, can the religious point(s) of view really claim objectivity, transcendence or absoluteness? Second, are the only games in town really religion and extreme relativism?
Claims to objectivity are the most bizarre to me. Objectivity is supposed to be the quality of something that is based on facts rather than thoughts or opinions. A system based on a single old book of myths then hardly seems objective. Furthermore, philosophers are insistent that one can’t derive an “ought” from an “is”, values from facts, so how can any system of ethics be fully objective? There is of course Rand’s perverse Objectivism, but that is more rationalization for selfishness than moral system, and it’s only objective by name. That is not to say that facts can’t inform moral decisions: they have to. But they can’t on their own be their foundation.
The claim of transcendence is that morality is somehow from out of the material world. This is of course entirely unconvincing to atheists who tend to find the supernatural to be an ill-defined, if not outright impossible notion. Kant objected to the notion of transcendence that something that exceeds the limits of experience is only hypothetically knowable. Real knowledge requires a tie to objective reality, and that seems to exclude the supernatural.
Transcendence is a rather hand-wavy way out from the problem of understanding morality: proposing an unknowable origin doesn’t explain anything.
Most of all, it’s a claim that falls to the Euthyphro dilemma: by declaring morality transcendent, you take the “it’s moral because it’s God’s command” option, which makes morality arbitrary. Which god are we supposed to believe, given that they give contradictory commands, and that their followers all claim, with similar arguments, that they hold the One True Faith? As a consequence, anything goes.
Believers usually reject the dilemma by declaring that goodness is God’s essence, that He is one with goodness. Of course, that’s more hand-waving, circular reasoning, and nothing more than a deepity. Their own argument actually forces them to answer the problems of evil and hell. If there is an omnibenevolent and omnipotent being, why are there earthquakes and tornadoes that indiscriminately kill and cause suffering for innocent people?
Then there is the absolutism vs. relativism debate. The main problem with this one, I think, is one of false dichotomy. It is hard to argue that there aren't moral issues that are relative, and others that are absolute.
For example, you would have to be out of your mind to argue against the fact that all things being equal, we ought not to harm other sentient beings. That’s an absolute, and there is no need of a God for that to be true. It does require the existence of sentient beings to make sense, but that’s another matter.
Reversely, most people nowadays would consider it morally harmless for an adult person to get a tattoo. However, Judaism has a commandment against it, and they are forbidden in Sunni Islam (but ok in Shia Islam). They are virtuous in Hinduism, as well as in certain forms of Christianity.
That not everything is absolute doesn’t imply that everything is relative. Reversely, that not everything is relative doesn’t mean that everything is absolute.
It should be clear at this point that there are other choices of moral philosophy besides Divine Command and an absolute relativism leading to nihilism. There are actually many other options. If you are interested in a great exposition and discussion of modern ethics, Massimo Pigliucci has a series of articles on the topic, of which this is the conclusion: http://rationallyspeaking.blogspot.com/2011/09/on-ethics-part-vii-full-picture.html
Even without understanding all this about the underpinnings of so-called objective, transcendent or absolute morality, we can empirically evaluate the initial claim, which boils down, really to “religious people are more moral than atheists”. Does it work? Well, not very well.
If morality came from God, since the US doesn’t imprison people for their religious affiliation, you would expect their prisons to be filled with atheists and almost empty of believers. You should even be able to tell which one is The One True Religion: it should be the one with the lowest crime rates. Quite the reverse is true. Atheists are dramatically under-represented in prisons, with 0.2% of the population (Denise Golumbaski, Research Analyst, Federal Bureau of Prisons, compiled from up-to-the-day figures on March 5th, 1997), against 4% in the general US population. This is often discounted as more of a correlation between level of education (with which Atheism is correlated) and delinquency, but one should see a massively opposite difference nonetheless if morality really came from God. If education was the only factor in this, you would expect to see the ratio between populations with higher education diplomas out and in prisons to be higher than the same ratio for atheists. The opposite is true.
This is just one example, the more general point being that the argument, if true, should be empirically verifiable, and it is actually verified that it’s false.
Whenever statistical data is published on a morally loaded behavior and its correlation with religious affiliation, religious people act at best the same as the nones, and at worst measurably worse. If religion is efficient at one thing, it may be in inducing guilt, but statistically not a change of behavior.
One last thing... When discussing those topics with religious people, I’ve often had the impression that they were committing a category mistake, confusing goodness with some kind of conserved quantity, like a substance. As if God created a finite quantity of moral stuff and injected that into people’s souls. This is also true of love, compassion, faith and many other things.
In the end, it does look like those arguments really are designed to de-humanize atheists, to justify a sense of moral superiority and to rationalize the adherence to a flawed system. After all, if one can really be good without God, what is God good for?