Here, in Sicily, we joke all the time about mafia, and bosses, and people buried in concrete pillars, and so on... but if one from another Italian region, or from abroad, recalls these issues, even while joking in the same way, we happen to get very much offended :-)
Here some kind of collective identity hasn't been elaborated enough through the years and overcome - both for niggers and "picciotti". I'm sure also something similar makes flames out from WASPs, scandinavians, aussies and people from the antarctica!