Gnostic Atheism? WTF?

[One Above All]

Wait a minute, didn't Neutron just prove you don't exist? How can I be sure?

His logic is under the assumption that you can't prove the existence of a god, and that gnostic atheism meant you were sure that what other people call "god(s)" don't exit.
My logic is under the fact that "god" is something that is left up to the individual; not humanity as a whole, since humanity can't agree on it. Therefore, you can prove the non-existence of an entity you consider "god", but you cannot prove the non-existence of every possible "god" concept, since there are as many possible "god" concepts as there are possible thoughts and things in the Universe. All anyone has to do is say "water is god". You can't disprove that. Maybe their definition of "god" is something with two hydrogen atoms and one oxygen atom. Under that definition, their god exists.