Want to know what's wrong with our history books? They tell the story of sin and conflict most prominently, and spend very little time on the positive figures and events which shaped our society. They teach us that our existence is all about war, hatred and greed, when the average person had next to nothing to do with such things. They tell the history of ambitious rulers, rather than OUR history. They teach us that we only matter so long as we are relevant to their power struggles.
Now that is a really damn good question anon.
Negative emotions like anger run at a lower frequency than positive or neutral emotional states, which makes people running on anger much easier to control by anyone at a higher frequency.