That's nothing but a propaganda bullshit by the media. There were many incidents at OAKA in the past to debunk that theory. Karaiskaki, Kaftanzoglio, and Pankrytio are at the same safe level as OAKA. As long as the police and security do their job, the violence problems can be avoided.
I think two good solutions would be to either have the game played outside of Greece, or have two leg final with only home team fans.