I don't think that even a "free society" can allow drug abuse due to the costs for society and the damage it causes.
You mean, like using a drug that will clear your sinuses, but has the side-effect of heart failure and death?
Seriously, smoking a joint, or even taking a shot of cocaine does not "abuse" make.
Or for that matter, getting drunk on alcohol, getting behind a while, and driving a kid to death?
The latter would indeed be abuse, and is not allowed, you are punished for such action, but does that mean we ban alcohol altogether?
What about the criminality which is caused by drug abuse?
Criminality is not caused by drug use, drug abuse - as in the car and alcohol above - is criminal in and of itself, and it thus does not cause criminality; whatever caused it came before.
Growing drugs, making it, and selling it, wouldn't be drug abuse, nor criminal if it wasn't illegal. Nor would it create "criminality".
When alcohol was illegal back in the twenties, there were massive amounts of criminals making and selling the stuff, and killing people over it. Now that it's legal, they're no longer around.
Besides that, a good society cares for the health of the people and drugs damages people's health.
Like the drug to clear your sinuses that can kill you?
This is simple matter of what's important, liberty or YOUR ideas of someone is or is not allowed live his/her life, because of YOUR ideas of what constitutes a threat to his/her health.
Me, I personally ascribe to the following:
"The only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others. His own good, either physical or moral, is not sufficient warrant."
- John Stuart Mill
On Liberty, 1859
That means any recreational drug should be legal.