You make it sound like your children don't have a choice whether to take drugs or not.

You could argue similarly by replacing drugs with anything (legal) that could harm your children. For example, do you blame motorcycle vendors for being responsible for deaths and hardship among the families of motorcyclists?

Drugs and motorcycles are certainly different, but it's a bit too easy to blame drug traffickers or dealers only without taking into consideration the parents and the social circle of the children.