Yeah, because the violent war on drugs has worked so well over the past 30 or so years! It's totally solved the problem!
All kidding aside the legalization thing its just part of the solution, along with treating drug addiction as a medical problem and not a criminal one. We could then take the money saved and invest it in infrastructure, job creation, etc. That way over time it would help lower other criminal activities and social ills not associated with the drug trade. There is no question that the illegal drug trade is fueling this gang violence, so taking that away would seemingly have a positive effect.