There are lots of legends about the Mafia in Sicily being chivalric, like Italian Robin Hoods. But I doubt it. Mafiosi, then and now, are parasites on society, like other organized criminals. In Sicily, the main job of the local Mafia boss, or gabboletto, was to protect wealthy estate owners and their land and water rights against ordinary people who made claims on them. The landowners wanted cheap labor and the gabboletti kept the contadini in line. In America, the Mafia's primary victims were fellow Italians--just as Jewish, Irish and Chinese gangsters preyed on their own kind.

In earlier times in America, omerta was generally honored because ordinary soldiers had no other ways to make livings, and so they knew if they kept quiet, they'd stay employed when they got out of jail. Also, a lot of the crimes they were involved in, like prostitution, gambling and liquor, were considered "victimless." Even drugs weren't a big deal as long as the victims were people society didn't care about. But in the Sixties, when drugs were widely abused and the victims were nice, white children of politicians, judges and law enforcement, big sentences were handed down. Later RICO piled double-digit sentences for even "conspiring" to be part of organized crime. And the Witness Protection Program gave rats a way out. So much for omerta...