This technically isn't the first occurrence of referee violence / potential violence. A referee pulled out a gun a couple years ago during an amateur match and another referee pulled out a knife during a match before subsequently being decapitated, both in Brazil.
I love this quote... "The Macerata police chief has said the ban was fully warranted, because Martiniello had failed to set a good example for youngsters." Well then, if it's all about setting a good example for youngsters, how do we go about cracking down on players surrounding and yelling at the referee in professional matches. Our "youngsters" watch that and it filters down pretty quick. (I know this has a only a very loose link to the thread...sorry...but every time I see it...which is always, I think about the example being set)
So player who was kicked out of game goes to seek out referee after game and violence occurs. If this was a youth referee, the initial response would be to blame the player because you are supposed to leave the ref alone. For an adult, why is the situation any different? Sure the ref is a dumbass for headbutting, but he obviously did not initiate the confrontation. If the player is close enough that he could be headbutted, it was not a friendly conversation. Player should be punished as well for, say a 6 month ban.