We tend to forget that the concept of the "nation-state" is relatively new in the larger scope of things. As humanity has grown in numbers, we have "progressed" away from our nomadic tendencies. This has led to all sorts of stuff that was possibly not envisioned, both good and bad. Some of the good things would include identification with place, a sense of attachment to our surroundings, generational stability. Some of the bad would be exhaustion of natural resources, sedentary life styles, the concept of "ownership" (rather than stewardship) of the land, parochialism, nation-states, and the list goes on.
What's my point? We have divided ourselves into all of these little units, to which we are expected to show allegiance, and when my unit cannot resolve its differences with your unit we may need to kill each other - even though you and I have more in common than we have to disagree over. And why do we do this? To control resources. To claim as exclusively ours what, by right, belongs to no one.
None of the "sacred concepts" upon which our nationalistic-capitalistic-materialistic world has been built are absolutely essential and inevitable concepts. They are all human constructs, created so that we can control the world in which we live.
Is anyone willing to stand face to face with a just god(dess) and admit that they killed another person - or caused someone else to do their killing for them - because of blind adherence to these artificial constructions? How about when the stakes are eternal damnation? After all, the commandment was Thou shalt not kill. It seems pretty clear to me. As the Onion put it: Four single-syllable words; what's to misunderstand?