I will tell my kids what I believe to be the truth.
The government is so zelous about prosecuting drugs like marijuana because they do not have a very good infrastructure to tax and regulate them. Since Nixon gave way too much power to the DEA, the Controlled Substances Act of 1970 provided them a direct pathway around the constitutional legislative stystem to designate the illegality of drugs without the need for pesky scientific or legal basis. As a result drugs used by Nixon's enemies (hippies) were deemed the most "dangerous" and therefore the "most illegal". Today the government spends more on drug enforcement (including police, DEA, border, customs, and 60% of our prison spending) than they do on education or healthcare. All for a failed political agenda in 1970.
I don't think it's a good idea to smoke pot. I have found through personal experience that it makes my friends boring, lazy, makes them act unintellegent, and it is expensive. I don't think it should be the government's choice, however. If you don't smoke pot cause it is illegal, you have not improved yourself at all, if you don't smoke it because you would like to remain the master of your own thoughts and senses then you are exercising true personal development. I don't think they should smoke pot, and pot happens to be illegal, the two are hardly related. I don't think they should eat trans fats either.
I am not pro-legalization, I am pro-constitution, and since illegalization is not constitutional, I don't believe action should be required to "elevate drugs" but rather to remove illegal political strategies against people who use them (removing their citizenship and political right to vote by making them felons for instance).
And yes, I have made parts of this rant to my 2.5 year old, and no he does not understand a word.