Why can't we all live in peace?

Right across the world people seem to be angry.  In the Middle East, the UK , the USA, nearly everywhere, people and nations seem to be angry.  

Maybe this is human nature, but I am sure most people everywhere want to live in peace with enough to eat and drink and a secure home. 

The main causes for conflict seem to be greed and insecurity.

Basically, people everywhere are the same.