No they don't. I've known MANY successful, productive potheads. You'd be surprised how many normal everyday people, managers, business persons, retail clerks, students, etc ... smoke weed. Also you're ignoring the fact that people already are living the life of a "druggie", and some are already dependent on the government. Legalizing it isn't going to create what already exist.
I don't, of the people by the people, for the people. The Constitution is not the government granting us rights, the Constitution protects our rights from the government.
Depends. It would be a situational thing, and more than likely involve a field sobriety test. There are a lot of chronic pain patients that have been taking opiates for years and don't get high, and drive to work everyday. Simply taking opiates doesn't mean you're going to be a pile of comatose gel.