[1] https://www.euda.europa.eu/publications/insights/internet-dr...
EDIT: Added citation for commenter who couldn't be bothered to use a search engine. Link contains links to multiple studies.
But how's that different from arguing that every crack dealer who doesn't cut their crack product is a utilitarian, net-positive life-saver?
Alice sells pure crack. Bob one street down adds fentanyl for the extra kick. It's a reasonable inference that Alice's clients, deprived of Alice, would switch to Bob and promptly off themselves. Does it therefore follow, that Alice-who-sells-crack is an upstanding, lifesaving even, member of society, who should be left free to sell more crack? If not, then what's the differentiation between Alice-who-sells-crack and Ross Ulbricht—what innovation has that cryptocurrency startup innovated, that makes it it a substantively different moral scenario?
Certainly, no crack dealer has ever, in the history of the US, tried to advance this specific utilitarian argument, which Ulbricht attached himself to (as Judge Forrest pointed out—it's a privileged argument of a privileged person).