Excellent description! Wife and I were stationed in Italy 67-69, just outside Rome. Was very surprised to find there were two Communist parties, the hardcore pro-soviet, and the ultra hardcore Mao Tse Tung supporters. There was also the Fascists, the Socialists, the Christian Democrats, and more splinters that you could count.
Our apartment overlooked a small plaza/traffic circle that had 5 or 6 roads spinning out from it. It was a blast to see the political parties there during elections. And recall, there have been more elections in Italy in twenty years, than in the history of the USA.
I have to say, I never felt the slightest animosity from anyone in Italy because of being American.
I too have spent some time in Italia, and have always been treated well by the locals. I had a few problems, especially in the area of Napoli, but by and large, the Italians were full of smiles and good cheer.
I anticipate the same, if I am ever able to visit there. But it looks like these demonstrators are trying to spoil a good thing.