For the only time in my history, I kind of agree with HRC. It”s really a combination of price premium due to illegal nature of drugs and “Says Law”; “supply creates its own demand” (famous French economist—the only one). If you legalize drugs the price drops to almost zero and the cartels and drug gangs are out of business. The bad news is most of the uneducated US population will be stoned most of the time—if they are not already. Kind of “Lose-Lose” proposition.
Even if you "lebalized" or decriminalized drugs, especially cocaine here in the US, I don't think it would have much of an impact on the violence and crime in the producing countries. In fact, it may even make it worse.
The situation for the producers wouldn't change that much. They'd still be gunning it out for the best territories, distributorships and growing areas. Hell, gambling in some form of another has been legal in America since the turn of the century, or earlier. Did that stop the Mob from making Tens of billions in illegal gambling operation the last 100 years? Of course not.
I do agree with your last point - it's lose, lose. Although, I think it's probably lose bad, or lose really bad. JMHO