I understand. We all have made mistakes in our past.
But the key premise amongst conservatives still remains. We do not want our government involved in trashing our young people with legal drugs.
Since kids report that they can now get marijuana more easily than cigarettes or beer, it follows that the best way to restict their access to drugs is to make them legal for adults only (thus giving those who sell to adults a disincentive to sell to kids - namely, the loss of their legal adult market).