Here is a verse that adequately summarizes the condition of our hearts:
Jer 17:9 The heart is deceitful above all things, and desperately sick; who can understand it?
Indeed, who can understand why good men do evil things; why fathers molest their children; how the eyes of otherwise faithful men could be diverted from their wives to images on a computer screen; why a man would want to have sex with young boys; how a maniac could kill five teenagers execution style? Why indeed? Because the heart is deceitful above all things, and desperately sick. We should not be surprised when we hear of evil and wicked deeds. We should be surprised that they do not happen more often. We are not by nature decent people, who mess up once in a while; rather, we are at the core rotten people who once in a while act contrary to our nature and do something good.
The darkness of this world seems to grow ever more pervasive the longer I live in it.