Alcohol is a very strong depressant too, and most of the heroin deaths aren't from people robbing houses that are empty while they are in withdrawal due to lack of money to buy heroin.

Heroin (and alcohol) also cause psychosis, which is probably the biggest cause for things such as spousal murder. Legalization is a weak argument when the only evidence is "It worked for Portugal!" or "If we take away the criminal organizations then everything will be well!". Instead of fighting the infinite number of criminals I'd rather we help the dudes who fucked up and now want to make their lives better.