I would think very hard about hiring or investing in someone who used marijuana, or who decided to sell marijuana (a bet with a big risk for very little reward), or who thought that using drugs was cool enough to include it on an application. Speaking from experience, marijuana is addictive, saps ambition, and makes it difficult to think hard and think logically. Anyone who has tried to code or do math while high knows exactly what I am talking about.
Wesley, obviously you have grown and been very successful since. I wish you only more success, and you are already far ahead of where I was at 19 (still smoking too much pot).
For me, I really don't give a damn what kinds of drugs people take beyond heroin, crack, meth, and others that have a clear history of detrimental effects on the individual. As long as you are rock solid and reliable, that's all that matters.
If you can be sure that someone is reliable, then you are right, there is no reason to have a problem with their drug use. When you are hiring someone or making the decision to invest money with them, you rarely know enough to be sure. Using drugs is a HUGE red flag there, and should say think twice before hiring this person / giving them money.
The difference is that I think very few people would say "Let's remove the stigma from alchoholism."