I call BS - let's see some evidence.
And even if all your claims were true, in the Land of the Free the most we can justly do is require accurate product labeling and leave adults free to choose their risks. Otherwise we'd have banned harmful substances like alcohol and tobacco.
I think casual use probably doesn’t do any more damage than casual alcohol use(.for most people) I’ve personally known heavy duty users of cannabis that have ruined their brains and their life in general. Also people who have fragile psyches can be sent down a path to psychosis with just casual use.
I do not think that any study has proven conclusively that marijuana causes brain damage.
https://www.webmd.com/mental-health/news/20030701/heavy-marijuana-use-doesnt-damage-brain#1
As for psychosis and schizophrenia, it’s good to remember that correlation does not necessarily imply causation.
People with psychotic problems often use cannabis - they often also drink to excess and or use other illegal drugs. They often do this in an attempt to self-medicate their underlying symptoms of mental illness. Of course the use of drugs and alcohol often worsen the symptoms. In the area of alcohol and drug addiction treatment it is called a dual diagnosis. For those people, just stopping the drinking and drug use is not enough if they also do not get treatment for the mental illness.
https://www.nytimes.com/2019/01/17/health/cannabis-marijuana-schizophrenia.html
There is more evidence that psychosis and schizophrenia has a genetic predisposition as if one has a family history of such, they are more prone to developing it regardless of cannabis use and conversely people with no family history who use cannabis are no more likely than others with no family history who do not use.
That is not my endorsement of using it or any mind or mood altering drug (excepting for those under medical supervision who need it), except for coffee - you don’t want to deal with me in the morning before my first cup of coffee : ),
It’s just that there is hysteria and hyperbole on both sides of the argument with one side with the old reefer madness argument and the other extolling cannabis as a cure all for everything under the sun.
Marijuana brain damage:
https://www.verywellmind.com/even-casual-marijuana-use-causes-changes-in-the-brain-67797