That seems like a loaded argument and a fallacious argument. You could have just as easily asked how you would be able to argue against the existence of a god if you believed in that god. The answer to your question (which you probably intended to be rhetorical, but it is not) is that the only way to argue against the existence of all possible gods is to not believe in any god. This is no more confusing a statement than a person arguing against the existence of unicorns while not believing in unicorns.
I would expect that if you don't like this response you would phrase an argument along the lines of the ontological argument.
I think you have tryed to over-emphasise the point I put forward, I was making the point in general to the article concerned which seems to convey a kind of aetheistic movement occurring which is in itself a contradiction of aethism itself, i.e. aethism is the abstention from organised religion.
Anyway, if you want me to put an ontological argument forward then I think a good analagous example is found in the bible itself when Jesus explained his miracles, i.e he said, anything is possible for the one who believes.
This indicates that if the belief and faith are strong enough you could easily levitate a coffee cup with your mind, however as your not likely to have that belief you will fail, but what if you did???