It is wrong to say that "Goverments prohibit drugs". The term, like I said in my pevious critique is too generic. Many citizens that don't know about drugs vote through Goverment to prohibit drugs. They would do the same in an an-cap society for any subject from pedophelia to caging torture.
It's true that in a voluntary society there would be some mechanism that stops things like pedophilia (well, pedophilia that gets acted on), but that's because it has a victim. If a voluntary society restricted you from doing something that had no victim, then it's not a voluntary society.
A better way to see this is to examine how the situation is handled in scientific research. Due to public opinion, most psychedelic drug research cannot get any funding. This is not because of "The Goverment" but because companies and colleges that do not want to see their reputation go to shit. It creates an endless circle of superstition and fear.
It's chicken/egg, which is maybe what you're getting at. Being illegal is part of why it hurts their reputation. And it's also part of why people can so stubbornly assume it's big bad scary stuff (it's hard to accept the government would do this for no reason).
When someone criticizes the war on drugs, they're not hyper-focused on state actors and dismissing that the attitude of ordinary people might contribute to it. They're trying to help change that attitude.