The reason for this is because God is carefully crafted and designed so as to be impossible to disprove; whenever God is disproved, religion just moves the goalposts. Which causes God to fall into the realm of 'it doesn't bloody matter.'
A more positive interpretation of this behavior might be to say "at least they're being flexible".
As I said in my previous post, the concept of atheism is often (and quite incorrectly) interpreted as an "anti-religious" (for want of a better word, "secular") movement as opposed to simply a movement involving the rejection of God/deities. As I'm sure you know atheism - in the colloquial sense, at least - is merely the rejection of anything "superstitious", that which cannot be or is yet not proven by scientific method. The issue with this misinterpretation is that I often hear of ironically fanatical "atheists" railing against religion as a whole, as opposed to simply railing against the concept of God.
Again, as I implied in my previous post, in modern times religion has far more significance than God does.
The point that I'm making by saying this is that people railing against religious dogma for its "flexibility", if you like, need to stop looking for a "truth" - that truth is clouded by your sheer humanity, and very similar rules apply to science, that practice that atheists hold so dear, as those that apply to religion (or the debunking thereof). "It doesn't bloody matter" indeed, because as far as I've seen theoretical physics is about as watertight as any organised religion has been in recent years.