If we have problems with substance abuse why would anyone want to make that worse?
What makes you think legalizing marijuana would worsen the "substance abuse" problem? If marijuana were legalized tomorrow would you rush right out and buy some? Or do you limit that prospect to others?
If you are not aware that marijuana does not belong in the category of "dangerous drugs" it is because you have been indoctrinated by drug warrior propaganda. The simple fact of the matter is marijuana is relatively benign. It is not addictive and there is no record in the annals of medical science of it causing death or illness. None. Zero.
You should understand that the only beneficiaries of marijuana prohibition are the pharmaceutical and liquor industries, the bottom lines of which would be seriously affected by legal marijuana, and the Law Enforcement Industrial Complex, a significant percentage of which owes its sustenance to the utterly insane laws against marijuana.
So rather than propagate the lies which clearly have been implanted in your mind you should give some thought to the many billions of tax dollars which have been wasted and are being wasted on prosecuting this relatively benign substance as well as the lives the persecution has ruined.
Marijuana prohibition is a crime against the American People. To not understand why is willful ignorance.