If drugs were legal, even WITHOUT government control, there would be advertising, and dealers who killed their customers would go out of business, while dealers who gave their customers excellent product that kept those customers alive and productive (meaning they could still earn a living so they could still afford drugs), would prosper.
However, in our society, the drug users could end up losing their jobs, but then government would jump in and support them, so there would be no negative consequences, and the dealers would still get their money.
Government is the problem. We have made every individual “to big to fail”. We won’t let a single person perish for their stupid, wrong, or bad actions. But without the fear of failure, there is no self-restraint, no push to improve.
Why work hard to “do better”, when everybody who doesn’t gets free stuff from government, paid for with a majority of what YOU made with your hard work? Unfortunately, eventually too many of us will be letting someone else to the heaving lifting.
You have glossed over the “... without doing any harm to others” part of the Libertarian philosophy. You have very quickly moved past the first cases of death cause by fraud. Until Libertarians can show how there allowing a pusher to sell drugs that can kill or maim ... does no harm to others, their arguments wont pass the most basic smell test.
As for companies firing people who use drugs, it is the very heart of Libertarian thought that enables them to do so. As the company is at risk due to loss of revenue, loss of productivity, increase cost of health care and risk of lawsuits due to failed products or performance. And since individuals on drugs show decreased mental and physical capacity, it is the BEST INTEREST of the company not to retain individuals who willingly engage in behaviors that are risky to the business.
As for the bad actors ... any doubt in your mind that a person on PCP, LSD or some other drug is a danger to others while driving? Making drugs illegal reduces the number of such occurrences and when someone is picked up while under the influence and sent to prison the government is creating a consequence to the individual before they impose their hurt, harm and danger on others. Or would you rather wait till some doped up drug head attacks some 75 year old grand mother and beats her to death in a fit of rage? Some people can protect themselves from a drug crazed lunatic. Some people cant.
How many people are you willing to sacrifice onto the alter of purity.