I won't argue with you that the "war on drugs" has some unfortunate effects, but I find that proponents of legalizing drugs haven't necessarily thought things through.
What you're wanting is for us to legitimize powerful, ruthless businessmen who have far-reaching influence in politics and an existing, entrenched supply and distribution network; a huge head-start over anyone else who wanted to enter the market.
Proponents of legalizing drugs say that we should tax them...what makes you think that people who didn't balk at bribery and murder would pay their taxes?
Assuming that they do start paying their taxes...legalizing drugs wouldn't get rid of the drug lords, it would simply allow them to openly buy the government of their choice to solidify their power, the same way big oil, the defense industry, etc. already do. How would any of this be an improvement?