You're assuming that the goal of drug prohibition is to reduce violence.

So you don't think we should prohibit anything? Should we just let people buy fentanyl by the kilogram without any repercussions? Sure, we should reform drug laws so that user's are not punished as significantly, but completely removing prohibition of drugs I think is pretty counterproductive, considering how the US already has a major opioid problem. Prohibition will obviously reduce drug use to some degree, so it's just a matter of balancing the costs and benefits.