The bulk of cannabis being consumed in this country is being used by people in their thirties, forties and fifties - not by teenagers. Many of them have been using it since the 1960s, the vast majority have not progressed to harder drugs, and I doubt if any of them would regard their lives as having been "ruined" or made "a living hell" by drugs.
As misdemeanours go drug use could, at worst, be regarded as a form of psychic masturbation. So, is it justifiable to jail someone because they are spotty, stressed out, boring and a bit of a tosser? I regard the idea as draconian, counter-productive, vindictive and a scandalous waste of public money.
Obviously there are very good reasons for making strenuous efforts to keep all drugs out of the hands of those under the age of 18. But if my 18-year-old son ever got into heroin I'd rather he got it from the local chemist for pounds 5 per gram than give pounds 50 to some dodgy dealer for something that might be anything.
Blaydon, Tyne & Wear