All of society's problems that are attributed to marijuana are really problems that stem from the laws against it.
There, fixed that for you. I'm fairly certain legalizing things like meth and cocaine wouldn't do much to aid the addicted. Just because one drug is harmless doesn't mean they all are.
Criminals are generally a symptom of larger social issues.
I don't disagree that certain criminal acts are products of desperation, for instance a thief stealing to feed himself or a young woman using fake ID to escape an abusive boyfriend, but your proposition assumes that if given the option, people will always do the legal/right thing.** This doesn't account for criminals who commit their crimes in spite of other options. The perpetrators of the giant economic con-job that ended up causing an economic melt-down were, in all likelyhood, quite capable of feeding themselves and their families without financial shennanigans. I have met individuals who financed their lifetstyles with criminal activity because, frankly, it paid better than working a legal job. Now, you could counter that this is an example of a social issue that needs addressing (wage floors, etc) but in doing so you remove some of the agency of the perpetrator, since the criminal is now only capable of taking the path of least resistance.
Again, I don't disagree that some crimes are products of social issues but saying that criminals generally commit crimes because they have no other choice is problematic at best.
**Yes, "right" and "legal" are not always equivalent and in several instances can be in direct conflict with one another but that's outside the parameters of our discussion at the moment.
Extending your line of thought, do you consider any US citizen who hasn't joined a police force, fire-fighting force, or military branch a coward? After all, said individuals aren't exposing themselves to danger when other people are. That must make all of those people cowards right? And please don't reply that you're against war because A) most military personnel would rather stay home with their families instead of being separated by an ocean for months at a time and B) that's moving the goalposts. This discussion specifically pertains to actions in a war theater.
*It's died down quite a bit in recent years, but I remember when the news organizations would run weekly death tolls of US service personnel.
I also have a sneaking suspicion we keep re-reading the same "classic" writers mostly out of tradition, even though their art is really not that high. Shakespeare, for instance, draws much of his comedy from fart jokes, fat jokes, synonyms for "penis", and the sit-com circumstances so widely derided by TV critics. His histories are fairly politically-charged as well, suited to fit the tastes of the ruling regents at the time.