The commander in chief admittedly used cocaine in his youth. He says he gave it up but he made the same claim about tobacco.
Would the use of cocaine (a licensed drug under your scheme) be automatic grounds for refusal of government employment?
In most instances, yes. I don't agree with you that all drugs should be treated the same. If they were, then childrem could buy alcohol and tobacco as easily as aspirin. Would that make any sense?
Coke gives you a big head and seriously impairs judgment. I wouldn't want to take a taxi, much less fly on an airplane, where the pilot was high on cocaine, or even had a cocaine 'hangover'. The hangover from coke leads to serious, sometimes suidical, depression.
To throw all substances with a potential for abuse into one category (DRUGZ!!! OMG!!!) is to continue the hysteria about them. Pot, alcohol, cocaine, methamphetamines and opiate derivatives all have a unique pharmacology with unique psychological effects.
I suggest starting with Marijuana legalization. Our last three Presidents have all admitted to using it in their youth, with no apparent lingering effects. (Don't get me started on Barry Soetero. His lingering effects are from the books and teachers he learned from, NOT from smoking reefers, LOL.)