I was in Athens in 2000, right around the elections. As a matter of fact, some political rally was actually going on at the hotel we were staying in. It was very passionate, but not the least bit violent, which given what you just said, is surprising.
I do recall being in Syntagma square where there was this big videoscreen set up for one of the candidates. We were on the corner waiting to cross the street when out of nowhere, this older man next to us screams really loud at the videoscreen, "F**king Crook! Criminals! All of You!", accompanied by various insulting hand signs. Surprised the hell out of us. He looked like somebody's grandfather. After this guy's short tirade at the videoscreen, he just kept walking & on with the rest of his life. I guess it was just a public release of frustration which no one seemed to notice except us.