Yes, nowadays its being used in crime, they buy and sell online and pay by bitcoin. Because its untraceable. So police cant get clue to caught them. I think its dangerous.
It's been used in crimes even when its just starting to gain fame in the deepweb, and so are other currencies. Every assets and valuable like money and gold or even goods and services can be used in crime, it has nothing to do with bitcoins system nor nature its working in too.
Well actually every criminal nearly use bitcoin to make money. This is also way some governments wants to stop it. On the other hand many people use it to make money.
So it is a difficult choice. They should disable the wallet of the criminals in my opinion. It is way better than.