Most negative consequences are caused by society and how the drug addict is treated, not by the drugs themselves.

Two logical fallacies; First, "use" does not equate to addiction by any means. The vast majority of people who try "addictive" drugs do not proceed to addiction or even regular use. Second, the costs to society are predominantly those imposed by society. The violence of the drug trade, the lives ruined by a drug arrest or conviction, the families broken up by incarceration of young men are all self-inflicted by society. Just having to deal with the ravages of addiction would be a welcome relief from all those things.