Using some form of mind altering substance is natural for human beings. Man has been getting high since the dawn of time. People need mind altering drugs like alcohol or marijuana to lose social hang-ups and gain the personal self-confidence to allow people to have fun, be happy and love life. So rather than asking of people impossible abstinence, it is better to ask they get only get high as much and as often as it takes for them to stay sane.
Read my whole article, Sometimes Moderate Drug Use is the Sensible Alternative to Abstinence, on the Addicts Not Anonymous blog.