Oh, but I
do condone it! Look, Rehnquist was certainly not the only, even an unusual, example of someone functioning extremely well, being extremely responsible and reliable while under the influence of mind altering drugs. The difference between his sleeping pill habit and someone else's illicit habit is only that he could go to his doctor and get professional help quitting w/o implicating himself in criminal activity.
What about Rush Limbaugh and his elephant doses of opiates? While I disagree w/ his politics and hold him in much disdain for some of his tactics, I don't think you can make an argument that he was anything but extremely reliable and high functioning the entire time he was swollowing enough opiates every single day to put a football team on the nod.
Then there are great historical figures from Poe (mrphine and amethyst) Dr. Halstead, father of modern surgery (injected cocain/heroin). The list could go on and on and on.
Point is, there doesn't seem to be any real correlation between substance use and performance. I think it may seem that way only because when people fall apart, we then go looking for reasons. If they happen to be a substance user we think that explains it. But what about all the other people using the same substances, to varying degrees of benefit or detriment, w/o falling apart? We have no reason to look for substance use so we don't find it so we assume it doesn't exist. Even though we know better on an intellectual level.
The most important thing in the programming language is the name. A language will not succeed without a good name. I have recently invented a very good name and now I am looking for a suitable language.
-- D. E. Knuth, 1967