Just as with anything that has a good side, there is also the bad side. We know that bitcoin is being used to do a lot of good and we cannot deny that some where on the dark web someone is try to buy drugs, pay for weapons, or other illicit purposes using bitcoins. I think that there is a role that individual like you and me can play in preventing this by reporting to the authorities whenever we notice that such thing is happening there is also the role that corporate organizations that deal with bitcoin can handle this. For example some mixers are used for this purpose. People who are in charge of mixers can have a strong policy against this and report suspicious activity to the authorities and not let them find out themselves because that is when the authorities get the right to label bitcoin bad instead of the act and the people.