That's like blaming water for people dying of cancer because of its role in all cells, healthy or bad.
Mr Gates, I respect you for you philanthropy, but you are getting old in your views.
I don't see street corner dealers and buyers scanning QR codes on their phones on the sidewalks. It's cold, hard cash out there and a very quick transaction. Statistically speaking, the online drug trade is negligible compared to the bigger picture.
Cash is also anonymous.