To be honest it was never about "forbidding their citizens to consume certain substances" whatsoever.. These bans were made to profit themselves and create economic rent on cartels that artificially pump up drug prices.
Marijuana ban was put in place in the States shortly after the prohibition to keep the DEA afloat afterall. Otherwise there was no substance to ban and the jobs in DEA will be lost.
Humans are entitled to do whatever they want and be personally responsible for it. Interventions arent sustainable and there is no way to draw a line.
You are right, I also heard this information before and it sounds pretty legit. I guess we are discussing the wrong question in this post. ;)
In an ideal world the legality of substances shouldnt even be an issue. Sadly it's not the world we're living in and it's run by governments that only budges under massive pressure from the populace. So I guess it's worth talking about it. In that bans on substances are outrageous and sugar/alcohol has fucked me up in more ways than cannabis ever will, why no ban on alcohol and processed sugar?