The fairness of prison sentences for drug abuse or dealing is a different debate, but I am not convinced drug users and drug dealers should make it to the army. It's not the war on drugs that creates drug users.
As the article states, it sounds like the Army is unconvinced “Has never smoked pot” is a sensible requirement either, given the rise of waivers. It’s hard to find an argument against pot that doesn’t apply to alcohol (except for “it’s illegal” which is only true because of the War on Drugs.)
Less convinced about the absence of decent job in a country where unemployment is at an historical low. There might be an absence of jobs in a particular city, but people can (and should) move then.
If you're unemployed and dirt-poor, moving is not likely to be something that's easy for you to do.
To me, this said more about how casual users think about drugs than about what they believe regarding Army regulations; a disparity between these outlooks that the Army (represented imperfectly by this drill sergeant) was unwilling to budge on.
Throughout history, the strongest soldiers of the strongest armies have always been on a kind of permanent high. It's uncertain anyone can withstand the hardships of military life, and of wartime, for any serious length of time, without drugs.