Drug-related gang violence isn't caused by drug use, it's caused by drug policy. Changing the policy so that it no longer creates ridiculously huge profit opportunities around the drugs in question does make the problems go away.

I completely acknowledge the importance of policy, hence the mention of the Netherlands progressiveness in the area. Explain how you measure the social impact of a drug without also measuring the social impact of the policy around the drug (or how the study in question did it), and you've answered my question.

This argument drives me crazy. You think the drug pushers are gonna say "ah shucks. no more profit in drugs. guess I better go to college and get a real job."

Trust me, they will find something else to exploit. Kidnapping in Bogota comes to mind. Crime won't go down.

Probably many would find something else, and that's a problem - but surely it can't be used as justification for not changing the policies. Legalization should happen gradually and with some kind of amnesty outreach program. But even if not: Crime like robbery would likely spike, but unless gangs quickly find a replacement product that's in similarly high demand (if there was one, wouldn't they already be serving it?) I imagine cutting off their easiest source of income would fairly quickly reduce their power to attract new members, purchase weapons, etc.

And even more quickly, since it takes a LOT more money, reduce their ability to bribe cops and judges.

Actually, crime went up a lot during the Prohibition period. Why would one illegal good differ so much from another?

EDIT: removed fragment: "This is extremely well known". I disagree with the parent, but let's keep the debate as civil as possible. My apologies.

I think you're underestimating the attraction of drug dealing as an occupation. Its profit vs. risk ratio is a lot higher than kidnapping.