As I see it you should present it as one possible truth, among many, sometimes condradictory truth. Spirits might not see themselves as demons beliving in the differences between the material and the void. Some demons might even promote infinite creation over an all consuming void. Present as many views as makes sense for the setting, and let the players or DM choose which ones they wish to believe. Some might choose that fatalistic viewpoint, while others might choose ones that are closer to espousing the virtues they prefer.