Social libertarians are really no different from the leftists that want to destroy society.
Legal drugs didn't destroy our society the last time they were legal (nor has the legal drug alcohol done so), and legal prostitution hasn't destroyed Nevada.
But rampant drugs and drug use destroys the culture. People will start to try them because they are available to try if not outlawed. The majority of the ghettos and cities with high crime rates have a drug problem. Drugs are bad. Who would want to poison the body and end up sick? You have to enjoy life not start destroying the one body you were given. If it is your choice fine, but people make an industry of it. If it is legal then the industry will flourish like in Amsterdam.