I went to a pre-season friendly, six or seven years ago, at Napoli (v Regiana) with my wife and two boys.
We were intrigued to see the fire brigade waiting outside the ground before the match (and then inside on the running track). We were also somewhat surprised to see many of the seats with burn marks or almost burned out completely. However, all became clear when the players came out. Flares rained down onto the pitch and it was obviously the fire brigade's job to put the fires out quickly.
We were sat amongst the Napoli fans. They were happy to chat to us, as I think we were a novelty. Half way through the first half a chap, I had been talking to, calmly stood up and threw a full bottle of liquid down on to the pitch. He missed the liner by inches. There appeared to be no reason for him to do it. It was just sport.
THIS WAS A FRIENDLY! They are mad!