I don't think that's necessary. The ONDCP recently put out some estimates on how much Mexican Drug Trafficking Organizations are making selling drugs to Americans. They estimate total revenues are $13.8 billion. They estimate that about $8.6 billion of that, close to 62%, is coming from marijuana alone. They say about $3.9 billion comes from cocaine, about $1 billion from meth, and less than $400 million comes from heroin sales. These are total revenues, not net profits. Marijuana is the biggest money maker for Mexican drug trafficking organizations. They bring in less than half as much from cocaine, and they're just the middlemen for cocaine. They produce the marijuana they sell. They have to buy the cocaine and import it so they don't make all the profits like they do on marijuana. If marijuana sales represent 62% of their revenues from providing drugs to Americans, then marijuana sales should account for a good bit more than 62% of their actual net profits because they make all the money from marijuana since they produce it and are not just the middlemen like they are with cocaine. If we just legalized marijuana, we'd deprive them of most of their income.
Not only would legalizing marijuana kill Mexican drug trafficking organizations cash cow, but it would make it harder for them to move their cocaine and meth and heroin too. Americans consume more marijuana than all other illegal drugs combined. The existing distribution networks for marijuana are massive and reach every corner of America. These existing distribution networks make perfect conduits through which to move other drugs, and that's exactly what Mexican drug trafficking organizations do. They use the same people to smuggle it in. They use the same people to transport it around the country. They try to move as much of their cocaine and other drugs as they can through the same people buying up their marijuana, and so often this is how their cocaine and meth and whatnot makes it to the street level dealer who is selling marijuana. If we legalized marijuana, those existing black market pipelines for marijuana distribution would disappear, and it would make it a lot harder for Mexican drug trafficking organizations to move their cocaine, meth, and heroin. In fact, the Colombians might just stop letting the Mexican control cocaine distribution in the U.S. because without the huge existing distribution networks for Mexican marijuana the Mexicans won't be in much of a better position to move Colombian cocaine than the Colombians themselves. Then the Mexican drug trafficking revenue would drop from $13.8 billion to less than $1.5 billion.
We don't need to legalize all drugs. Legalizing marijuana alone would reduce Mexican drug trafficking organizations to a shell of what they are today. They'd be deprived of the lion's share of their profits and their main pipelines for moving the hard stuff would fall apart.
I could go along with legalizing marijuana.