Because of one simple fact. There is something, an issue, that exists here, just as it exists anywhere else, as far as I know.

Two people might come across one another, and in doing so, they will find this answer.

"I am different from you."

That is why conflict occurs, why there is strife, why there is war. [The utter joy and love he has for that last word is obvious in his voice as he speaks it.] And as long as this continues to be the case, there will always be a lack of harmony.