I'm genuinely curious: to atheists seeking proof, please could you give me some examples of proof that would lead you to believe that the Christian God exists? (Bad analogy warning) It seems to me like some people are trying to prove that 1+1=2 and some people are trying to prove that love exists. It's like there are two parallel conversations happening so of course you get frustrated because you're just not talking about the same thing.
I consider myself a scientific atheist, in that I see no objective evidence for the existence of god that isn't just as readily (often more readily) explained by non-god-related natural processes and laws. Were objectively measurable evidence that supported the existence of deities to appear, I would then approach that question using the scientific method. The scientific method never 'proves' anything absolutely unquestionably 'true', nor is it meant to. It CAN lead to absolute disproof and therefore our ability to discard incorrect hypotheses, and move on to test the next hypothesis (thus advancing knowledge).
ETA: sorry, Nick_Miller, I see you are trying to move the conversation on, and I posted nearly simultaneously with your post.
Let's say that every single person on earth simultaneously experienced a vision, which they described more or less identically, of a giant tentacley, glowing deity figure that said, "I am Cthulu, kneel before me". Now, if I were to have such a vision, I would first assume that I had some sort of hallucination from a natural cause (inadvertent drugs, brain tumor, etc.) But if everyone around me, and indeed everyone on earth had this simultaneously, this would fall outside our current understanding of natural explanation. I would have to consider the real possibility of something outside our current experience (which could be, but isn't necessarily, a deity) causing this. Then scientists all over the world would presumably investigate formerly unthinkable, but still NOT supernatural, alternatives. Perhaps humans experienced a simultaneous biological response to some sort of extraterrestrial phenomenon? Etc. In the end, if there was no evidence of e.g., extraterrestrial or other natural phenomena causing the vision, I would likely settle on provisionally accepting the reality of a god calling itself Cthulu to be 'true'.
It's important to note, however, that while I might come to personally accept the existence of god(s) as provisionally true and act in the world with the understanding that Cthulu was out there (just as I do with robustly supported scientific theories), this acceptance would always remain slightly provisional and contingent on no further better explanation for my vision ever becoming available.
The real problem though, though, is that the way most of humanity views god(s), they are by definition supernatural and not subject to disproof (see Sagan's dragon-in-the-garage analogy for the simplest explanation of a non-disprovable idea). Therefore, any evidence that came to hand that didn't fit the Cthulu hypothesis (which would lead scientists to reject Cthulu as the actual explanation for the vision), would be accepted by most believers as Cthulu working in mysterious ways, or Cthulu operating outside of natural law, or what have you.
Alternatively, believers can (and do) offer me all sorts of 'evidence' of god(s) existence, but unless this evidence is disprovable, then it remains essentially meaningless to my view of the universe and how I live my life. I assume that the fact that Christians don't believe in, e.g., fairies and gnomes, or the ancient Greek gods, or Cthulu, doesn't worry them, right? Why would the lack of evidence of something cause them to ever even think about that thing? Likewise, lack of objective evidence of a Christian god means that it isn't a question of concern in my life, and the only reason it ever crosses my mind is that our culture privileges it above millions of other such ideas.