A lot has been said about how the various Biblical authors did not hold to the concept of creatio ex nihilo or creation out of nothing. Of course, the alternative to creatio ex nihilo is creatio ex materia or the idea that the world was created out of existing materials much the same way a table is created out of a tree or a pot is made out of clay.
I stumbled upon an interesting quote from an early Christian Father named Justin Martyr who also seems to have rejected the idea of creatio ex nihilo in favor of creatio ex materia.
And we have been taught that He in the beginning did of His goodness, for man’s sake, create all things out of unformed matter (Ante-Nicene Fathers, edited by Philip Schaff [Christian Literature Publishing Co., 1886]1:165).
So, the rejection of creatio ex nihilo by Latter-day Saints is not a valid reason to dismiss LDS as non-Christians. By that standard, Justin Martyr would also have been a non-Christian.