Synthesized drugs are harmful as it's made from pure chemicals.
Nature grown drugs like cannabis, shrooms and opium aren't healthy for you either but are a lot better then MDMA, meth and coke etc.
What? You would rate opium as a better choice than MDMA? That is a claim you are going to want to justify.
Going further there is no foundation for calling artificially created substances more harmful than naturally derived ones.
That is an argument for banning cigarettes, not for legalising weed.
I never quite got that line of logic.
Scene as it were
So we live in a free country after a fashion.
"We are going to either ban or maintain historical bans because the harm done by said substances, or at least the risk of harm, is so very high"
Fair enough, might question the efficacy of that but it seems to play under the law so go it for now
"As everything is dangerous under the right conditions, or wrong conditions as the case may be, these are substances we deem suitably harm free to allow for consumption, possibly restricted by age, activities you can do under the influence of them or something. These are the metrics we have used to quantify harm"
Excellent
[someone does some science]
Going by those metrics these restricted substances are demonstrably less harmful than the ones you allow. The remedy for this as we all kind of agreed we like consistency and logic to underpin laws far more than "magic book governed by elites says so" or "boss man's gut feeling" is to either further restrict things or to remove those restrictions.