You previously discussed the homogeneity of the Faith of the Seven, but is there any historical precedence for the relationship between the followers of the old gods and those of the Faith? Barring Baelor the Blessed’s contemplated crusade, it seems very relaxed.

Not really. The early stages of the Faith’s growth is pretty close to the rise of Christianity, albeit one more reliant on the Arian Goths and without a Constantinian establishment. 

But historically speaking, the parts of Europe that remained pagan were either missionaried into Christendom or brutally crusaded against – we think of Crusades as entirely focused on the Middle East, but Charlesmagne’s Saxon Wars and his campaigns against the Avars and Slavs set the pattern for the Wendish Crusade, the Livonian Crusade, the Estonian Crusade, the Prussian Crusade, etc.