First, judging from your interpretation of our responsibility, Springdale must have a very tight-fisted control over the actions of their citizens. Thakria gives its citizens free reign to go cause pain, bloodshed and personal acts of violence, as they see fit. Only if they do so in the name of the city, use city resources or try to invoke city protection/support for their actions, involving citizens involuntarily, are those actions seen as a city issue.
Nauthsiiir, while a respected citizen of Thakria, used no city stockrooms, no city resources, no city troops in his actions. You could just as easily be making these demands to the Sorcerers or to Lord Nostradamus' order. You choose Thakria because the former is not lucrative enough to try to pressure, and the latter is simply too intimidating. Thakria \"supports\" the stripping of an insignificant child insomuch as they aren't inclined to rob a citizen of possessions he earned on his own.
Your crude argument that Thakria is responsible for the actions of one loudmouthed runt and someone who sought to silence him opens up a lovely convoluted avenue of city interaction. Shall we attribute every action of Springdalians to Springdale? Judging from the mob mentality that our neighboring village forces and propagates, perhaps we should.
Written by my hand on the 27th of Paglost, in the year 1160.