I think if the state can make a compelling argument as to regulating a substance like a drug, then let them make it, and if it falls under their enumerated powers to regulate it, then regulate it. I have no problem with that notion, though we could debate the efficacy of regulating a substance / turning the substance into valuable contraband.
The problem, however, with most pro-prohibition arguments for pot is that in their zeal to push their cause, the pro-pot-prohibitors typically conflate - very, very, very greatly - the "societal dangers" of pot by attributing the societal dangers of other, more pernicious drugs (like your heroin, coke, LSD from above) to marijuana as well. Or else they attribute other things that are bad or harmful - say, a car crash that kills young kids - to pot, because it's logically possible to drive a car while stoned.
The real world doesn't work that way, you see. You can't factor out an extremely complex societal equation with all sorts of unpredictable, dependent variables in it to, say, "if you're for legalizing pot, you're also for kids killing themselves in massive car accidents while driving stoned."
’ the pro-pot-prohibitors typically conflate - very, very, very greatly - the “societal dangers” of pot’
I see the same zeal and similar arguments used to demonize pot as those used to demonize guns. Exchange the word gun in many pot threads, and folks would be agonizing about their natural right to self defense. The analogy is not perfect, but the emotions are. People are afraid of losing their safety and losing control, no matter whether they are liberals or conservatives.
I’m not a pot user for the record. As long as I have my full natural rights, I’m ok with more freedom in terms of its legalization. There will be some period of teeth knashing at this point just as there is after every gun restriction is lifted.