I am interested in how you have reached your position of atheist, then. If you mean atheism in a broad sense, but admit that a broad argument cannot be presented against theism,... does this put into question, the surety of your atheistic position?
I am interested as to why you keep referring to how atheists use of the word "atheist" generally. It seems like you are pointing out that "atheist's" get to hide behind a vague term, while no one goes by "theist". Their classification that they identify with is far more specific as to what their worldview is (Muslim, Christian, Orthodox/Reformed Jew, Hindi, Buddhist, etc.).
But, that merely speaks to the term "atheism" itself being vague (just as you have shown "theism" to be with this thread), or, at the very best, a semantical argument.
But, if my assumptions about the beliefs in question in the OP are incorrect, forgive me, as you have repeatedly refused to state, specifically, what those beliefs are (beyond "theism in general", of course).