When would-be bank-robbers decide to walk away from a caper, we don't wring our moralizing hands that these miscreants hadn't seen the light. No. Society is content enough that they decided to walk away from doing evil today.
L.P. founder P.T. Barnum, cases a joint with Mumbles and Scarface.
Of course, we have laws against stealing because such an act deprives another of their right to property.
Laws against the possession or use of marijuana are, indeed, designed to "enforce morality onto those who do not share it," since the mere use or possession of marijuana deprives no other person of his Constitutionally-enumerated rights. The only possible justification for such a law is either that smoking pot itself is immoral or that doing so may lead to some future immoral act (most which can be imagined are likely already prohibited by law).
My Church holds that it is never moral to do evil so that good may result. Depriving someone of his liberty so that some future imagined immorality does not occur is the worst sort of evil I can imagine.
"God willed that man should be 'left in the hand of his own counsel,' so that he might of own accord seek his Creator and freely attain his full and blessed perfection by cleaving to him."