Is it drug use per se we care about, or the negative consequences of drug use? What if more people used drugs but there were fewer drug-related crimes and accidents?
It is probable that there would be more drug use if drugs were legalized. (This is acknowledged in the article.) However, its not clear at all if related crime and accidents would go up. Looking to the example of alcohol prohibition, crime went sharply down when it was re-legalized. Many people die as a result of alcohol use while driving every year, so it seems possible that accidents from driving on drugs would increase with legalization. (This could be mitigated to some degree by harsh penalties for driving under the influence.) In general, I am puzzled as to why alcohol should be treated differently than other drugs.