The Golden Dawn flag waved by supporters of APOEL Nicosia during the football match against Olympiacos in Piraeus is a Nazi symbol. It is the symbol of a Nazi, fascist criminal organisation which tries to pose as a political party. It is a Nazi symbol because of Golden Dawn's Nazi ideology.
The issue isn't a typical matter related to UEFA policies about political messages in football. It's more than that. The shameful gesture of APOEL fans to wave the flag of Nazis consists a political and social issue. The symbols of Nazism and fascism, the symbols of Golden Dawn, have no place in football stadiums. They have no place anywhere.