That's what I've said several times with no response from you: alcohol is more addictive than marijuana, more violence-increasing, and the only one of the two that can lead to fatal overdose.
it may reasonably be surmised that, in the aggregate, the greater marijuana use that would follow general legalization would lead to a greater burden of marijuana abuse and mental illness.
Facts trump surmises: as I said, while marijuana use has risen over decades there has been no corresponding increase in overall levels of schizophrenia.
marijuana has well-proven dangers
As does alcohol - greater on a number of fronts.
Not enough is known about the epidemiology of schizophrenia to provide evidence for the argument that you suggest. Yet the proven effect of marijuana in causing and triggering schizophrenia and prompting relapses in schizophrenics makes for a sound reason for keeping it illegal.