yes bitcoin can be used for good and every currency can be use for good .
That is right. The bitcoin is just a tool, just like the gun, that can be used for good causes or bad causes.
Well because of anonymity of bitcoin they can use bitcoin for dark market places where you can found all illegal that you can buy there.. using bitcoin..
This is one of the problem in bitcoin thats why some people are still not trusting bitcoin to invest because its risky..