the real effect of what is described on that show would be the opposite. you aren't taking away the 80% of crime where the proceeds go towards procuring the drug. you aren't taking away inter-supplier conflict. and you are decreasing the available drug turf thus increasing competition between suppliers and raising the stakes.

in short:

* same crime to supply addicts is there * inter-gang violence is still there * premium on drug territory increases, thus violence and competition increases