Why does the world need good people?

The world needs good people in order to make good things happen. We need good people to help change and better the world. Without some good people in the world, the streets would be filled with crimes.

At the same time, the world needs bad people. for instance looks at the 9/11 tragedy. Not only was everyone sad and crushed due to the fact that thousandths died. But not only was it a tragedy but it made us the people stronger and more aware. Not saying it was good that it happened, but only that we need bad people to make a good person out of someone.