Ra's Al Ghul: Gotham's time has come. Like Constantinople or Rome before it the city has become a breeding ground for suffering and injustice. It is beyond saving and must be allowed to die. This is the most important function of the League of Shadows. It is one we've performed for centuries. Gotham... must be destroyed.---Batman begins.
Update: Maybe Linderman had a point. In preventing the explosion, the heroes unwillingly unleased a virus that would wipe out the human race!