Anyone making the above argument does not understand atheism nor it's position fully. One key point is missing - the burden of proof lies with whomever is making the claim that God does exist. An atheist doesn't claim there is proof for or against the existence of God. When an atheist says there is no God what he probably means is - there is no evidence to support the claim. That is why many of us have such a strong conviction that God doesn't exist.
“That which can be asserted without evidence, can be dismissed without evidence.” ― Christopher Hitchens
Neither scientists nor Christians can prove the existence or non-existence of God due to the unfalsifiability of the claim. Scientific theories must be falsifiable to be considered valid. By proof I mean providing evidence produced by the scientific method. Falsification is an important mechanism of the scientific method to separate superstition and pseudoscience from real science.
I'm sure you can find quite a few dogmatic atheists in placs like YouTube claiming they can prove God doesn't exist by, for example, reciting news articles about a baby being struck by lightning ("If God exists, and he is good, then why did he allow this terrible thing to happen?!!".. and so on). Bad events, however, do not prove one way or the other whether God exists (e.g. consider the "God is mysterious" statement). You can't test stuff like that scientifically, you need palpable evidence. This is also when classifications like strong and weak atheism comes into play. These youtubers often have a distinct belief that god doesn't exist (strong atheism) when atheism in general (weak atheism) is defined by it's lack of belief without any claims or denials being made. It's a subtle, but important difference. Ironically, strong atheism has belief-without-proof in common with religion.
So as an atheists can I rationally prove, absolutely, that there is no God? Of course not - no one can. Atheists don't have to prove it because, as I mentioned, the burden of proof lies with the religious folk. It's not simply a matter of copping out and passing the buck either - from an atheist point of view God is a non-factor in the natural world until solid evidence to the contrary is presented, and it never has. Not even once. It doesn't make sense to make claims about something that cannot possibly be known. People can speculate, sure, but that's a far cry from truth.
On a personal note, I call myself an agnostic atheist because I find that it's the most rational position for me. For example, I answer two key questions in the following manner:
Question #1: Do you believe in God?
Answer: No - I see no reason to believe due to lack of evidence. (Atheism)
Question #2: Does God exist?
Answer: I don't know if a god exist - because God is by definition unknowable. (Agnosticism)
Which I guess qualifies me as both atheist and agnostic. There is a lot of overlap between agnosticism and atheism so they are not mutually exclusive. When casually asked if I believe in God I tend to simply say no without elaborating, just to avoid the headaches. I also skip the agnostic part when asked about my lack of faith and simply go with atheist; unless, of course, I'm invested in a deeper conversation about religion. This lazy way of labeling myself as simply an atheist is something I have in common with many others, both weak and strong atheists alike.
