We go around preaching to others not to tell us how we should protect our families with firearms but the minute anything crosses our minds that we think others shouldn't have... well, we start preaching about what is good for society.
Personally, I think nothing has been worse - surely more destructive to the body - than alcohol. We finally realized that if adults want it... well, 'to thine own self' as long as you do not inflict yourself on society (drunk driving... violent acts under the influence, etc). There are drugs worse than alcohol. Let's focus on them and not continue to preach what 'we think' is good for society on something many states have already realized is innocuous.
You’re pathetically naive if you think that gangs and illegal commerce in pot will just “go away” with its legalization.