Thanks for the headsup Brehme!
^ I studied for one year in Thessaloniki, and used to live nearby the PAOK and ARIS stadium. So I've experienced those images all to often.
@Brehme: In your opinion, what reasons could there be for such aggressive behaviour by the Thessaloniki supporters?
Response to corruption, plays a big part.
And just nothing else to vent on.
When it comes to PAOK fans, it's also some sort of delusion that they are being targeted but no one really cared about them, if anything it's considered that they are jealous that they're not the corrupt ones, very very similar to Olympiakos fans, who are the corrupt ones
Panathinaikos, AEK, Aris and Iraklis fans aren't at all like this, at least historically. And obviously in terms of majorities that make it reasonable enough to generalize.
There are various sociopolitical matters at play, subconsciously. I'll give you a small display, without going too deep into it.
We have a saying "the goat of my neighbor can die..."
It comes from a short story of two neighbor farmers. One of them had a goat and was too happy about it. An angel appeared and asked the farmer with the goat what he wanted to wish for. He said he wanted another goat, so that his could have a friend and he'd double his business.
Then the angel went to the neighbors house. He told him that he could grant him a wish, to give him a cow, a goat, a pig, anything he wished.
The farmer said: "I want my neighbor's goat to die". This sick mentality is deeply ingrained in Greek society and its root goes back 100 years. (Maybe more if you challenge the reasoning which has to do with 1923, google it as it's way off topic and sensitive).
As for collective mentalities:
Panathinaikos fans want to be the greatest Greek team.
Olympiakos fans want to be the greatest team in Greece.
Sounds the same, yet the difference is immense. Panathinaikos fans want Greek football to be good enough so that the team can challenge once again for Europe. Olympiakos fans do not care about how useless Greek football is as long as they can collect trophies at the expense of everyone else.
You then have AEK and PAOK, where K stands for Constantinople. Both are refugee clubs. You have AEK, with a dream of returning to their home town. Another saying we have is "better first in the village than second in the town". First can be exchanged with king etc. PAOK fans on the other hand are content to be kings of Salonica. That's their mission. Ironically, in total trophies won in all sports they were 3rd until a few years ago and possibly are barely 2nd now. Either way, their ambitions are just that. Aris on the other hand was a cosmopolitan club (supported by the large Jewish community as well) and had ambitions to be the most important club in Greece. And now they have to deal with PAOK. (And they're also run by corrupt people that made them into a vehicle for other purposes but since society is sick, they're just too happy that they're above PAOK for a change and can go to Europe finally).
Due to the 1923 situation, there were two mentalities in Greece. The Ψωροκώσταινα mentality, which talks of Greece as some small, sick state in between two worlds(east and west), typically backed by Royalists. And then you had the pro-western factions that want to be...European. The 1910s displayed this at all levels if you're interested in that. One would not expect to see this carry on with football in one of the most apolitical* countries in terms of sports, but a lot of people who have studied this have reached these conclusions and they're hard to argue against.
* While Panathinaikos is supposed to be the elite's club and Olympiakos the port side workers, and the Aris/PAOK situation is rather similar, this has stopped being a thing since the 50s. And there are no "left wing" or "right wing" clubs either. At least not to their core, some fanbases due lean one way or the other.
But yeah back to your question, I think the mentality clashes, the general sentiment on what their club stands for, the corruption and the stupid laws that made fans blood boil since there's barely a movement of fans in away games for over 15 years all brings this result. The fan move ban is just a result of the corruption anyway.
But for PAOK in particular, this is a club whose fans are chasing ghosts, want to present themselves as macho and above all, they are overzealous.