Atheists, by and large, are making no claims, therefore they don't have anything to defend.
Atheism's only claim is that there is insufficient evidence for the existence of God or gods.
I find it quite hard to agree that an atheist, posting on a religious debate forum, making arguments from an atheistic worldview is making 'no claims'.
The idea that you can completely abstract 'atheism' from any other context, connotation or signified meaning and turn it into a purely neutral taxonomy that is devoid of any implicit complementary meaning goes against the standard usage of language.
People will use the word 'Christian' for example, when almost no specific beliefs are uniform to all people who self identify as Christians. What can you actually say that is categorically true about
all Christians?
For the vast majority of atheists, atheism is part of their ideology (Ideology defined as how someone explains to themselves the way things are and the nature of things). Beliefs don't exist in a vacuum in nice neat compartments with no cause/effect relationships and no interrelation.
Many beliefs exist as part of a continuum/matrix, so while the term Muslim conveys very little that is uniformly true about all Muslims, there is
some degree of connection between all beliefs that are part of this Muslim continuum. Radical Salafism is not the same as mainstream Sunnism, many of their beliefs specifically go against orthodox Sunni jurisprudence, but we wouldn't say there is
no connection between them. We don't hold them as synonymous, don't blame the average Sunni for views they don't hold, but we can admit there is some linkage between them. Most people wouldn't say that radical Salafism has
nothing to do with Islam.
Atheists don't have to be materialists, humanists, communists or anti-theists, but an expression of atheism is an ideological statement. Once you have accepted that you are an atheist, this influences many subsequent decisions about the nature of existence. It doesn't per se lead to any of them, but just as there is a link between moderate religion and fundamentalist religion, there is a link between atheism and anti-theism. Just because atheism has no intrinsic link to communism, doesn't mean that an atheistic worldview didn't influence communism.
People might say 'atheism makes no claims', but when actively professed it does make claims about the nature of the world. This is especially true when it is used in the context of a specific discussion.
There seems to be an almost pathological need for many atheists to deny that there could be any link between an atheistic worldview and any negative or oppressive action carried out by an atheist. Even when it is part of an expressed ideology, as in the case of many communists for example, an atheistic worldview is never a partial cause of their behaviour. It may not have been purely atheism that caused it, but an atheistic worldview is certainly related to it.
Just as a religious belief may lead to extremism, so can an atheistic worldview. They are not synonymous, but they are related.
Many atheists here (not all), have certain sacred cows that activate a reflexive defence response if ever questioned. These tend to involve the idea that atheism frequently relates to an ideological position, that it can ever be connected to violence, or that the Enlightenment, 'science' and 'reason' can legitimately be connected to illiberal or totalitarian ideologies.
Correlation is not necessarily causation, but that doesn't mean it never is.
Many atheists here will refuse to accept that communism has any connection to the enlightenment and that de-Christianisation of USSR of post revolutionary France could possibly be inked to an atheistic worldview. Instead, "Atheism is just..." "Stalin was raised a Christian..." "Worshipping the 'Goddess of Reason' in Notre Dame is not connected to atheism..."
I'm an atheist (although I dislike the word and don't normally use it), and I don't see any problem with acknowledging that there is a clear link between an atheistic worldview and certain negative consequences in certain situations. None of them are just atheism, but there is a link. Obviously, I don't hold myself responsible for these, or see them as being intrinsic to atheism. Just as I don't see any negative consequences of religious belief as being intrinsic to religious belief in general.
It is true for all groups that they wish to minimalise their own ideology, so that negative points can be deflected as 'not part of my ideology' while at the same time maximising the range of ideologies they see as oppositional, giving them a better target to hit. At the same time, they all like to deny that they are doing this.
When you participate in a religious forum, and make arguments regarding atheism, you are adopting an ideological position though, and can't pretend it's just some neutral, value free classification. Acknowledging this is neither attacking atheism nor supporting theism.