Your argument seems a bit inconsistent. While I generally understand the spirit of what you're saying, claiming that "over 50% of the US population has tried it to little effect" doesn't seem any less anecdotal than your example of the friend trying "X" 3 or 4 times.

All these substances should be assessed scientifically for medical risk, and empirically for societal risk.

Asking for dealers to be shot on a drug-by-drug basis is a bit sensationalist. Drug dealers simply respond to demand in the market. They sell whatever people are buying -- they don't have personal agendas about which drugs to sell. Demand for drugs is notoriously inelastic.

I'd modify your last statement to say that people tend to dump all illegal drugs into one bin, and legal drugs into another. Most everyone seems to think legal drugs are safe, but people tend to be split on illegal drugs (some think they're all the worst things ever, others seem to falsely presume they are all reasonably safe).

Personally, I think there needs to be more and better education across the board. The legal/illegal distinction is rarely meaningful and detracts attention from a proper comparative analysis of drugs and their risks. For example, fentanyl is more powerful than both heroin and morphine, yet is a legally prescribed painkiller. Similarly, Adderall has a family-friendly reputation for helping kids study, yet along with its use come many of the same risks associated with speed. This is not surprising, because they are in fact the same thing -- amphetamines.