The problem is not BItcoin itself. It's the society. The World needs to be balanced. Good and bad work together for the survival of the world. So those are beyond our limits we can only reduced it but can't eradicate it.
Criminals are always present in every time and society, they are using different currencies for their different purposes, they may have used Dollar pond, Euro and any other currency which find it suit for their activities, they will surely use bitcoin if they find it more easy and convenient for their activities. not a single currency is specially created for the criminal people.