Atheists who act as a group to displace religion as part of their 'belief system' necessarily have a religion themselves. Atheists who work to undermine faith systems and win converts do so on behalf of their own religion. Atheist activists are thus active on behalf of a religion.
Response:
The most visible form of atheists' activism is probably arguing against the value of religion and theism. More and more atheists are standing up to not only publicly admit that they are atheists, but also to say that neither religion nor theism have anything to offer which makes them very necessary or attractive. People can not only lead good, interesting, and meaningful lives without them, but might in fact be better off if they try. Does arguing against religion mean atheism is a religion?
Of course not — the above myth is wrong in so many ways and on so many levels that it's difficult to count them all. For one thing, the mere fact that someone abandons religion and adopts some other belief system in its place does not mean that they have a religion. That's nonsense. People who claim otherwise are essentially denying that it's possible to not have a religion, a claim rather like saying that everyone must have a god. Both claims are false: people are not only able to live without religions or gods, but people who try generally find that they can live quite well without religions or gods.
Second, the mere fact that someone with a non-religious belief system seeks to convince others that this is better than religious belief systems does not therefore mean that their belief system must be religious — the definition of religion does not include an urge to convert. Some religions don't seek converts while many non-religious belief systems do seek converts.
The fact that someone doesn't try to convert others to their belief system doesn't mean that they don't have a religion. Hinduism and Judaism, for example, don't try to win converts yet they are obviously religions. At the same time, the fact that someone does try to convert others to their belief system doesn't mean that they do have a religion. Democrats and Republicans try to win converts all the time, and obviously they aren't religions.
Third, this myth is self-contradictory: if arguing against religion means that they have a religion, then it's being claimed that atheists have something because they are arguing against it. Where's the sense in that? If atheist activists have a religion, then how can they argue that there is something flawed and wrong with religion? Even if we are generous and allow that perhaps there could be something to this, religious theists who repeat the above myth don't try to explain how or why. Either they don't recognize the contradiction they are accusing atheists of having, or they do recognize it but don't think it's worth dealing with. Either way, I think this shows that they haven’t given serious thought to what they are saying.
Fourth, it's rare to find atheists acting as a group to do much of anything, much less displace religion in society. Atheists who do argue against religion, religious beliefs, and theism often do so as individuals acting on their own. There are atheist groups involved with arguing against religion, but most atheists don't belong to them, and it's an open question how much real influence they have over atheists generally.
This sounds like a criticism, but it's not. The fact that atheists don't act in concert and don't all join atheist organizations is simply one of the many signs of how atheism isn't really any sort of belief system, much less a religion. It's a demonstration of the degree to which individual atheists move in their own ways and don't merely take direction from atheist leaders. It's a sign of just how different irreligious atheists are from most religious theists, and thus of just how incredibly wrong myths like this really are.
