Quote from : The Hobbit: The Desolation of Smaug Movie

Legolas: It is not our fight.
Tauriel: [reluctant] It is our fight. It will not end here. With every victory this evil will grow. If your father has his way, we will do nothing. We will hide within our walls, live our lives away from the light and let darkness descend. Are we are not part of this world? Tell me, Mellon, when did we let evil become stronger than us?