The world has always been, and still is, filled with cruelty:  From crucifixions, the Mongols, the Inquisition, and slavery; to America's Cherokee, the KKK, pandemics, and the Holocaust; to Hitler, Stalin, Mao, and Pol Pot; to Rwanda's genocide, Sarajevo, and Saddam Hussein; to violent religious extremism and 9-11; to North Korea, Iran, and Syria; to drug lords, organized crime, sexual deviancy, and 20-something aged men with severe psychopathy...  

But the world is mostly filled with people trying to fix it.  

We must keep trying.  And we have to keep at it, even when things are "good" lest our history should repeat itself.  It's our eternal mission.