Why there will always be war? Easy, because there will always be humans. (I feel like I am repeating myself badly everytime I start a post)
We don't want to be equal, we want to have people under us, that's why the idea of communism(class system and everyone should have the same etc.) didn't work. Why should we live with less if we could have more? Why should be agree with someone when we know we are 100% right(->religion) or even ignore him, and not force them to their luck?
Humans are lazy, egoistic persons who mostly care about themselves, but hey, what's new?