This paper doesn't directly support what you said. In the abstract it says: "With Silk Road functioning to considerable degree at the wholesale/broker market level, its virtual location should reduce violence, intimidation and territorialism."

There are 3 mentions of the word "violence", one says that the typical internet drug dealer is typically less violent than their offline counterparts but this doesn't meant that gangs will just let others take away their income because the new dealer is dealing out of a living room instead of on the street. Silk Road was B2B, as the paper mentions. But those businesses still need to get their drugs to the end user which seemingly happens on the street.

So it's an assumption, not a proven fact.

Harm reduction (IRL, safe injection sites) reduces violence.

That way, a registered nurse/healthcare official who has a job/career to lose if someone overdoses. Nothing is stopping a random dealer using a DNM from cutting a batch with fentanyl, and anonymity means they can fake reviews and hide it