What evidence led you to that conclusion? Since alcohol is more addictive than marijuana, more violence-increasing, and the only one of the two that can lead to fatal overdose, I conclude exactly the opposite.
Caffeine, for example, has a substantial risk of dependency but a minor risk of harm for almost everyone. That is why soft drinks given to children are permitted to contain a dose of caffeine.
Nevertheless, high doses of caffeine are toxic, and it has a potential for dependency and to compound the effects of alcohol, nicotine, and other substances. Experts differ as to the risks of high caffeine energy drinks, but enough cases of toxicity and death have been reported that no one with a lick of sense claims that they are without any risk if consumed to excess.
Yet rarely does caffeine impair anyone's work performance. Alcohol, marijuana, and opioids though all have enough risk of impairment that few organizations tolerate employees working under their influence.
Similarly, tobacco has a high risk of addiction and long term harm but a relatively small risk of harm in the short term. Alcohol, in moderation, is relatively benign, with psychological and genetic factors though disposing some to excess and to addiction.
As for cannabis, it causes short and long term impairments, especially of memory and attention, and there is a strong body of evidence that cannabis use is associated with schizophrenia. Broadly stated, not only are those who have or who are predisposed to such mental problems prone to use cannabis, but there is growing evidence that, in teens and genetically susceptible adults, cannabis use can trigger schizophrenia.
Moreover, the evidence suggests that schizophrenia patients with a history of cannabis use have a significantly higher burden of care than non-cannabis users. And not only does it seem that, for teens and the genetically susceptible, cannabis use increases the risk of schizophrenia and increases its severity.
Do not take my word for any of this. Do your own research through Google, PubMed, and medical texts. I have read enough on the subject and seen enough of the harms of marijuana use among my contemporaries to oppose its use and to fear the consequences of the wide scale legalization now underway.
For any who think marijuana is harmless and ought to be fully legal, I urge you to consider the consequences of: more doctors, lawyers, airline pilots, and other professionals who are heavy users; of roads loaded with semis and other vehicles driven by heavy users; and more schizophrenics wandering around loose and using marijuana, alcohol, and other drugs. That seems to be where we are headed -- and it will not be for the better.