The thing I find interesting about this debate is that conservatives take a position on guns that making them illegal will not reduce gun violence or reduce the number of criminals with guns. On the other hand, the same folks will argue that keeping pot illegal will somehow keep it out of kids hands or somehow be effective. The only real difference I see between legal and illegal in both cases is whether the distribution mechanism is above board or criminal black market.
Marijuana is a plant. Should Valerian plants be illegal since you can make Valium with them? Ginseng?
Your comparing an intoxicant to a hunk of metal and finding no difference?