Actually you can get pretty close, bearing in mind that you can't actually prove anaything (that's why we have beyond reasonable doubt). Simply ask them to define their god. They can't because as soon as they do they run into allsorts of problems of things like free will, the benevolence of an omnimax god etc. You can also look at the scriptures that they quote, namely the old and new testament and show the large number of contradictions that is the word of god. They also run into the problems of interpretation too. Oh this bit of the bible is metaphor and this bit is literal, how does anyone know when no one can know the mind of god? You only have to look at the ridiculous stories in the bible to see how crazy it is. When you match this with the lack of historical evidence for jesus then things don't look to rosy for a christian god.
I don't see anyone on Hexus ripping into christians. I'm sure hexus would clamp down fairly fast. The problem with christian posters is they do not offer a reasoned argument and tend to ignore the questions that others post. This happens not just on hexus, it's endemic.
As for Atheist fundamentalism I find this laughable. It's exactly these kinds of attacks by the religious, using the language that religionists spout to their own kind, that find the derision that is warranted. In the article linked, as so often is the case, the religionist's argument is a non sequiter. Just because someone changes christmas to winterval does not mean that they are atheists, just the same way that atheists do not, in general, seek to ban christmas. I've no doubt that the council involved are part of the lefty PC brigade who, for some unknown reason, are trying to be "inclusive" and think, wrongly, that christmas offends people of other religions (let alone atheists). I have no wish to ban christmas or impose any restrictions on worship just like the majority of atheists. The phrase "militant atheist" also gets bandied about, which too, is ludicrous. When you see large aggressive demonstrations by atheists, persecution of the religious, murder of christians for being christian then "militant" or "fundamentalist" tags will be appropriate. The funny thing is that most atheists are the exact opposite of fundamentalists, most seem to be humanists/rationalists and these are the last people to engage in this sort of activity. It's the religious that are projecting their own values onto people they simply don't understand and falsely see as a threat.
The christians are using the old persecution complex (just as muslims do) when those of us with reason speak up. "You don't agree with us and are saying it. Help we're being oppressed!" The hammer and chisel of logic and critical thinking is happily chipping away at christianity and the christians don't like it. Well perhaps they ought to do more to convince they rest of us rather than moaning and whinging.
It reminds me of this which is in relation to the US