I agree with you on libertarian grounds that, in principle, a person should be free to ingest whatever he likes. However, looking at civilized society as a whole, I don't see making most controlled substances legal useful. With the exception of marijuana and a few anxiolytics (which I'd encourage to be legalized), I think they'd be counterproductive to the working order of a society. Society needs someone to clean the toilets, and do other labor intensive jobs. But if you have a legally accessible ticket to happiness through drugs, why go to work?