>So it would logically follow that we do need one less substance to dumb down society and that criminalizing alcohol for adults would be a good policy. Problem is, that conclusion is false, and therefore so is your premise.<
It does NOT "logically follow" that "criminalizing alcohol for adults would be a good policy". Therefore, neither my conclusion or premise is false.
The concept that legalizing marijuana is an unnecessary and net negative societal impact, stands on its own.
Insisting that if we don't take that step, then we MUST roll back other societal 'net negatives', is a thought process void of logic.
It's entirely logical; if the criterion for "X should be criminalized" is "X has societal 'net negatives'" then that's true whether X is marijuana or alcohol (or eating unhealthily or getting too little sleep).