Taking note of the above discussion about the unfortunate connotations attached to the phrase “anti-theist” (once again, in part the product of the lack of rigour of everyday language) …
I prefer to describe myself as being in opposition to treating unsupported mythological assertions uncritically as fact. Hardly a pithy phrase, but one that far more accurately represents my true position. If someone can provide a succinct encapsulation of that, I will of course welcome the effort expended, and acknowledge copyright accordingly.
The point being that we here, if we are to be rigorous on the matter, are opposed to a failed epistemological process. One that has demonstrably failed, because at no point has uncritical acceptance of mythological assertions ever led to genuine, substantive knowledge. Instead, it’s led to many errors, the persistence of fallacies, the promotion of wilful ignorance and, at worst, the elevation of deliberate discoursive duplicity to a purported “virtue”.
Indeed, the fun part is, that I’m on public record here as not being opposed to theism per se. Indeed, several of my regular readers will be aware that I’ve posted some interesting speculations on the nature of any god type entity that might genuinely exist. See some of my braneworld cosmology posts for an example that many here may have found amusing when I posted it. For newcomers, the thread in question is this one, and the speculative post therein is this one.
What I am opposed to instead, is the idea that my entirely proper suspicion of unsupported assertions contained in pre-scientific mythologies, purportedly constitutes some sort of cognitive and ethical deficit, a scurrilous insinuation that is all too frequently deployed by the mythology fanboys. Indeed, the proper rules of discourse tell anyone familiar therewith, that suspicion of unsupported assertions should be the default modus operandi. Furthermore, that suspicion should be deployed universally.
The regulars won’t have to look very far on the forums, in order to alight upon pernicious examples of the consequences of failing to deploy said suspicion, particularly when said failure is selective and agenda driven, and which brings into sharp relief where the real cognitive and ethical deficits lie.
occasionally. 
Oh make mine a tes though, not much of a coffee drinker.