Myth:
If an atheist says they lack belief in God, yet actively seek to undermine theistic proofs and promote atheistic principles, then their actions are consistent with their beliefs; namely, that they actively believe that God does not exist. Atheists who say they lack belief in God, or disbelieve in God, yet actively attack theistic proofs and seek to promote atheism, are acting according to their beliefs, not their non-beliefs or their "lack of belief."
Response:
Many religious theists, especially Christians, resist defining atheism as simply the absence of belief in gods. There are a variety of reasons for this, but the main one seems to be that it makes it too obvious that the burden of proof or support lies with them, not with atheists. One tactic for arguing against the standard definition of atheism is to claim that atheist criticisms of theism and religion demonstrate that atheists must be acting on behalf of a belief, not some mere lack of belief.
There is some truth to this, in that merely not believing in any gods will not inspire a person to critique religion, religious beliefs, or theism. Merely lacking a belief in the existence of any gods is insufficient cause a person to get involved in any debates with believers about the nature of gods or about the reasonableness of theism. The mistake made by Christians who repeat the above myth lies in their failure to distinguish between what atheism is, broadly defined, and what an atheist happens to do.
Not everything which an atheist does can be attributed to their atheism — not even those things which are in some manner connected to their atheism. Some atheists attend sporting events, but this doesn't follow from their atheism and can't be claimed to be part of atheism. Some atheists enjoy photography, but this also has nothing to do with their atheism as such.
These examples should be pretty obvious, but in principle they are no different from examples which are less obvious. Some atheists are Buddhists, but this doesn't follow automatically from atheism and it can't be claimed that being a Buddhist is part of what atheism is. Some atheists are nihilists, but this also doesn't follow from atheism and can't be claimed as part of being an atheist. The same is true of opposition to religion and theism, a preference for liberal, Democratic political candidates, or anything else which is not a direct consequence of atheism. These beliefs and preferences may or may not be common for atheists, but they do not derive from atheism itself.
All of this becomes even more clear if we talk about theism instead of atheism. Some theists are Christians, but being a Christian doesn't automatically follow from being a theist and we can't say that Christianity is part of the definition of theism. Some theists pray, but we can't claim that this is part of the definition of theism. Some theists attend worship services on Fridays, but this also isn't part of the nature of theism. Obviously not everything which theists do is necessarily part of the broad definition of "theism" which applies to all theists. This includes even those activities which are closely tied to a person's theism and other theistic beliefs.
I doubt that any theist would dispute this and I doubt that any Christian would for a second imagine that because some theists worship God on Friday, that therefore this is part of the definition of theism. That, however, is effectively what Christians are doing when they promote the above myth about atheists — the individual elements are different, but the structure of the argument is identical. I don't understand, then, why they fail to realize this.
Some atheists do actively believe that no gods, or at least common conceptions of the Christian god, exist. Some atheists actively criticize theistic arguments, theistic beliefs, and theistic religions. These atheists and others do indeed act on the basis of what they believe, but what they believe goes beyond mere atheism — just as theists act on beliefs which go beyond mere theism. Atheism is only the absence of belief in gods, regardless of whatever other beliefs individual atheists act on beyond this. Theism is only the presence of a belief in one or more gods, regardless of whatever other beliefs individual theists act on beyond this.
