Atheists should we be arguing with the abrahamics about creationsism?

Shouldn't we require before the ideas of creationism are even discussed that the abrahamics provide convincing proof that their deity is "the deity". After all there is no historical verification of most events in the bible--it is readily apparant that many of the biblical stories and precepts were plagarized from the sumerians and egyptians. (the much older gilgamesh epic becomes noah, the much older king sargon story becomes moses, the much older babylonian creation myth of men from clay becomes genesis). If we change tactics from arguing about "god" to requiring some sort of convincing proof that theirs is "the deity" would the concept of creationism even need to be addressed?