I'm not necessarily saying drugs are good for society, but I am saying the costs of the drug war are greater than any benefits. If there are any benefits, which I haven't seen evidence of.
Brawls and such are the result of the choices of a portion of people who happen to use drugs. Most people who drink choose not to get into brawls and shootings, etc.
Prison is very expensive, and the usual narrative says that it's just as easy to get drugs in prison as outside of prison. We still have to pay for healthcare of drug users when they are in prison, but we also have to pay for the prison. Also, many of the users do contribute to the economy in their lives, but can't while they're in prison.