First: Blockchain transactions are only accepted when they’re added to the blockchain, so participating in the blockchain necessarily directly enables the drug (etc.) transactions in a way which isn’t true for fiat or commodity currencies.

(I happen to have the opinion that almost all drugs should be legally available in some form for personal use, but that’s a different argument; partly but not solely because I think legalisation will help to stop criminals getting the money).

Second: inverting group membership like that is poor logic.

Consider for example, that the fruit of atropa belladonna is poisonous. The fact that most poison isn’t derived from belladonna does not change this.