Millions of people have died because the government has banned certain drugs. Whereas the number of people who have died because of a drug not being banned is zero. It seems like a clear tradeoff to me.
http://en.wikipedia.org/wiki/Fen-phen had a body count before it was banned. Such cases are rare, but that means the system is doing at least part of its job.
People died because they took a dangerous drug. They didn't die because the drug wasn't illegal.
If you want to cut down the number of people taking dangerous drugs, ban doctors from prescribing non FDA-approved drugs and ban companies from marketing them. However, I have only contempt for people who want to put their fellow citizens in jail for making their own medical decisions.