Is "God" (just) an ethereal concept?
I do not see how atheism can be scientific in any way. "Atheism is, in a broad sense, the rejection of belief in the existence of deities" (WP:Atheism) The thing is you cannot prove nor disprove this statement. Its is an ethereal concept with no bases in scientific measurement by tests and observation.
First, I take it that by "this statement" you refer to "God does exist" and the like.
Secondly, I understand your argument as roughly saying: Since "God does exist" is not truth-apt, neither is its negation "God doesn't exist".
If I may refer you to an historical antecedent, this point was made a long time ago about disputes over meaningless terms by Rudolf Carnap. What is often forgotten, is that Carnap made an interesting observation precisely over the meaning of the term God. He pointed out that the word is multi-layered, as it were, so that "God" is not just an "ethereal concept":
Another example [of meaningless terms] is the word "God." Here we must, apart from the variations of its usage within each domain, distinguish the linguistic usage in three different contexts or historical epochs, which however overlap temporally.
In its mythological use the word has a clear meaning. It, or parallel words in other languages, is sometimes used to denote physical beings which are enthroned on Mount Olympus, in Heaven or in Hades, and which are endowed with power, wisdom, goodness and happiness to a greater or lesser extent. Sometimes the word also refers to spiritual beings which, indeed, do not have manlike bodies, yet manifest themselves nevertheless somehow in the things or processes of the visible world and are therefore empirically verifiable.
In its metaphysical use, on the other hand, the word "God" refers to something beyond experience. The word is deliberately divested of its reference to a physical being or to a spiritual being that is immanent in the physical. And as it is not given a new meaning, it becomes meaningless. To be sure, it often looks as though the word "God" had a meaning even in metaphysics. But the definitions which are set up prove on closer inspection to be pseudo-definitions. They lead either to logically illegitimate combinations of words (of which we shall treat later) or to other metaphysical words (e.g. "primordial basis," "the absolute," "the unconditioned," "the autonomous," "the self-dependent" and so forth), but in no case to the truth-conditions of its elementary sentences. In the case of this word not even the first requirement of logic is met, that is the requirement to specify its syntax, i.e. the form of its occurrence in elementary sentences. An elementary sentence would here have to be of the form "x is a God"; yet, the metaphysician either rejects this form entirely without substituting another, or if he accepts it he neglects to indicate the syntactical category of the variable x. [p. 4|5] (Categories are, for example, material things, properties of things, relations between things, numbers etc.).
The theological usage of the word "God" falls between its mythological and its metaphysical usage. There is no distinctive meaning here, but an oscillation from one of the mentioned two uses to the other. Several theologians have a clearly empirical (in our terminology, "mythological") concept of God. In this case there are no pseudo-statements; but the disadvantage for the theologian lies in the circumstance that according to this interpretation the statements of theology are empirical and hence are subject to the judgment of empirical science. The linguistic usage of other theologians is clearly metaphysical. Others again do not speak in any definite way, whether this is because they follow now this, now that linguistic usage, or because they express themselves in terms whose usage is not clearly classifiable since it tends towards both sides.
Rudolf Carnap, "The Elimination of Metaphysics Through Logical Analysis of Language", 1932
Please note that one doesn't need to swallow the whole verificationist framework in order to find this analysis pertinent for the question at hand. The distinction between metaphysical and mythological meaning isn't necessarily based on any strict verificationist assumption. We can certainly enlarge our understanding of empirical existence to include theoretical concepts (electrons, strings) and social facts (the existence of five dollar bills, being married to someone). We can even enlarge our understanding of existence to the non empirical domain to include fantastical concepts (unicorns, etc.), such that e.g. in "some sense" we can say true things about Sherlock Holmes.
I'd think that Dawkins & Co. attack the "empirical" viz. "mythological" meaning of God and the question of its existence and in that respect negative claims of the kind "God (most probably) doesn't exist" or "I don't believe in the existence of God" make sense.
Arguing that this kind of "empirical meaning" of God is nowhere implied in the theological discussion today seems to me to miss the mark. For it is certainly not the case that "the whole thing is based on faith" as you say: The existence of God is supported by references to any kind of phenomenological effects in the domain of human experience. Or, to take the semantic spin: They submit that sentences about God are truth-apt.
Now, the proponent in these discussions can always retreat to a "metaphysical" (in the above parlance) understanding of God, but in doing so the whole concept looses much of its punch and relevance. And I would submit that Dawkin & Co. have no particular problem with this metaphysical understanding of God, that's not the target they are after.