Imagine

Imagine there's no countries,
It isn't hard to do,
Nothing to kill or die for,
No religion too,
Imagine all the people
living life in peace...
...
And the world will live as one

~ John Lennon ~

Lennon wrote these words and though there's no doubt about how nice the song is, I wonder is that what we really want? Being different is an integral part of human nature, if we were all the same what would be the difference between us and the millions of computers that we use. Again borrowing from Bono's song "we're one but we're not the same", I think describes us as a race.
peace and religion are subjective and to some extent conflict is required to keep our minds going. Without this we would just be droids walking around without and personality of our own.
Assume for a second that everyone in the world is "one" would we be able to appreciate it? Would we not question the ideas of the people around us and if we did would that not stir up argument and maybe even war (in the worst case). It isn't possible to be completely "one" with everyone on this planet, knowing our nature.
The Olympics were started as a measure to stop war. They're great for entertainment now, but we're kidding ourselves if we say that its helping us stop conflict. On or off the field, conflict is an integral part of humans.