@irontoenail - To some extent I agree with you, but I think there are certain professions where drug testing should be mandatory and expected. Pilots, for example, should not be doing drugs and I don't care if they are only having a joint on the weekend or not. The same goes for anyone who is going to be operating machinery. If they don't like it, they can find a different profession.
I think doctors, nurses, policemen and possibly teachers should be included in that as well. When you are trusted with the lives of other people I don't think doing drugs is a good look.