I don't consume any drug but alcohol (socially). However, I have knowledge that buyers can buy any kind of drug trustfully and anonymously thanks to bitcoin (whether in legal or illegal markets).
IMHO, this isn't bad for bitcoin, nor for the world. Bitcoin give true liberty to the people. I also think we should better help people with drug abuse problems rather than ban drugs.
may be no one can know about the fact that either bitcoin is really using for illegal activities like for buying drugs or not because bitcoin is a anonymous currency and no one can no about the activities for which bitcoin is being used.