Firstly, Paisly isn't your capital, secondly Paisly isn't your only city, it's one of about four that you have including one stronghold that can also support a capital, thirdly as far as I am aware you weren't founded in Paisly, and fifth, Aurvandil conquered Paisly when you were too incompetent to keep the city and too proud to accept Aurvandilan food to feed it. The only real comparison you can make is to say if Evanburg was a city and we lost it due to starvation and then you make a neutral realm in it. You cannot say Candiels and act like it is a fair comparison as it is our only city, our capital, the place where we were founded and it wouldn't be a region we lose due to incompetent administration but instead through military conquest. There is a world of difference.
You are obviously completely ignorant of what Paisly means to the Véinsørmoot. It is the jewel of the Maroccidens, it is the birthplace of Maroccidental culture, civilization, and society. Melodia was born there and started the long tradition of Maroccidental Republics and societies. From there Nobles spread to Terran and the Dragon Isles and eventually nobles passed through Paisly to come to Terran to create Barca.
Furthermore, there is a history of fighting to protect the city from Southern invaders and conquerors. We fought long, drawn out wars against Madina to keep the city when they refused to release their claim on it. Aurvandil taking the city is just ripping open all of the old wounds of Southern Imperialists always trying to impose and conquer in the Maroccidens and the small realms vying to stay alive and keep their land. You are Madina reborn.
It isn't different at all. Sure, it's not technically the "Capital" of any realm. But as much as Candiels is the birthplace of Aurvandil and their culture and their history, Paisly is the same thing, except with an even deeper and longer history and significance, to the entire Maroccidens. There is reason why Terran is fighting so hard for regions that aren't even theirs to begin with.
Literally, conquering Paisly and putting some insulting puppet realm there (and here I thought relations couldn't get any worse) is the worst thing you could have ever done for relations with the Maroccidental realms short of just taking Terran, Barca, and D'Hara off the map.
