I'm not saying at all that hemp is a new substance. I'm just saying that the two drugs have different histories and that's why one is legal and the other is not.
Okay I hear you. Their respective history explain why one is legal and the other isn't, but that doesn't justify it nor is a viable reason not to change it.
Saying "Alcohol is legal? Well... let's legalize marijuana too then." is a wrong assumption.
It's not totally "wrong" but not judicious and a bit oversimplifying.
See it this way : if alcohol didn't exist and the number of marijuana users was the same, the question would still needs to be asked. Does it really have to stay forbidden and criminalized if a large portion of the population feels like it's okay to use it ? considering the cost of prosecution, the cost of the "war on drugs", the fact that the actual way to deal with users doesn't help them at all nor stop them from using, the illegal traffic etc...
Truth is, from todays health standards, Alcohol should rather be forbidden than Marijuana legalized.
I'm not sure what you mean by health standards. But people have the right to consume their brain, body and health as they wish, we're not in a "perfect health dictatorship" from what I know. Plus assuming that every users eventually use to the point of getting sick is pretty inacurate.
Abusing something is certainly bad. But because some people abuse something, it doesn't mean the reasonnable ones should be forbidden to use that same "something".