Government created "adverse section" in the war on drugs

Art Carden writes,

“But these drugs are so dangerous!” people might contend. Indeed, they are. But this overlooks the fact that drugs have increased in potency as a response to government crackdowns. Which would be easier to smuggle: $1,000,000 worth of marijuana, or $1,000,000 worth of cocaine? $1,000,000 worth of cocaine can be packed into a much smaller space than $1,000,000 of marijuana. If we decide to fight drugs, what is likely to disappear from the market and what is likely to end up all over the market? Low-potency drugs are likely to disappear. High-potency drugs—like higher-potency marijuana—are likely to stay. According to Milton Friedman, “crack would never have existed. ... if you had not had drug prohibition.”

So in a effort to drive all drugs out of the market the government has has only succeeded in creating a situation in which more dangerous drugs are driving less dangerous drugs from the market. Certainly a very "adverse selection".