Where the rubber meets the road, this advice is useless. According to this, I can use Cocaine like coffee to get a job done or go out dancing with my wife when I am tired and do not want to. Teach this to the children, that it is just a venial sin and it will they will go the way of the 1960's.
I guess you didn't actually read it (or comprehend). Cocaine has an extremely high risk of addicition and would therefore fall under that prohibition.
Secondly, here you go again with the "just" a venial sin garbage. Nobody's advocating venial sin. Jone says that it's venial if there's no proportionate justification, but no sin at all if there's proportioniate justification. So, if you could take cocaine without the risk of addiction (not possible, from what I understand), and it didn't compromise your reason, and you needed it to get your work done, yes, it would be justifiable ... and NO sin at all (not "just" venial sin).