you know, you sound like a fascist when you talk like that. fair enough if you believe drugs are detrimental, but you cant make threats to get him to think the same way you do, and what you think isnt always right, or relevent to him.
let him do whatever the fuck he wants, and he'll only have himself to blame. its okay to express that you disagree with his decisions in a respectful manner, but you cant threaten him about it.