Money is used to buy weapons, drugs, and other crimes. Gold and other good jewelries can also be used to exchange some kind of drug as like Bitcoin it can be used too, but things are used depend on how people used them.... Don't put pressure on Bitcoin..
I think it's not a problem, people already know that not only bitcoin can be use for illegal activity, this will not affect people's thinking about the negativity of bitcoin because most of the people who are attracted to bitcoin tend to think about the benefits of the bitcoin and not the negative that it brings.
Yes, it can use this as an illegal transaction because we are anonymous but there's a lot of solution to avoid this as illegal activity because the surrounding is too secured and the forum is legit for people perceptions.