Prohibitionists

"They pull a knife; you pull a gun. He sends one of yours to the hospital; you send one of his to the morgue."
--Jim Malone (The Untouchables)

Prohibitionists never seem to learn. Seeking to restrict voluntary trade between buyers and sellers inevitably fails. People who want to trade will trade. Black markets inevitably arise to satisfy latent demand. And because prohibited trade is by definition criminal, black markets tend to attract...criminals.

Crime becomes more organized over time and frequency of criminal activity increases. Law enforcement in turn develops harsher measures to deal with illegal activity. Criminals respond in kind. And violence escalates.

The irony, of course, is that prohibitionists generally seek to reduce violence rather than to increase it. But they are the ones initiating violence against people who wish to peacefully trade.