Only out of context. Part of the fundamental contract between the US Government and "we the people" is that our freedom of action and choice is only supposed to be restricted when there's a clear danger.
The clear danger being to society - the clear danger to the person taking the drug is irrelevant (although it will become relevant when we become a socialist nation for the purposes of medical care).
If something is x dangerous and legal, then making something that's x-1 dangerous illegal flies in the face of that basic precept.
Negative. If X is dangerous and legal, and X-1 is dangerous and illegal, it illustrates that perhaps X should also be illegal, not that X-1 should be made legal although also dangerous.
Making the point that X does more damage to society as an argument that therefore X-1 should be legal as well is poor logic. If the argument is on the basis of danger to the person (which marijuana proponents insist it is), then arguing that more dangerous things are legal is simply arguing that the more dangerous things should be illegal too.