And during the prohibition, black market flourished. The business will always be there. The question is do you support organized crime or do you support taxing to cover harm reduction and safety for people (buying from non-criminal sources, tested product etc)

Currently your stance is to provide money for organized crime

As has been stated already, past prohibitions didn't really work out that well.

I'd also add that 'mind-altering substances' is casting a really wide net, and could be argued to include stuff like caffeine.

I personally like Portugals approach of decriminalisation, because I think criminalising these substances usually hurts people addicted to them most, while helping those wanting to profit of addiction.