In regards to the Sansa/Jon debate, while both of them had sound logic behind their viewpoints, I think Jon was more right than Sansa. Also, there was room for a compromise but after Sansa publicly contradicted him, Jon was backed into a corner where he had to put his foot down. He was crowned literally minutes beforehand; he couldn't start his reign by getting backed down by his sister in front of his new subjects.
Once a civil war is over, the most important step is securing the peace. Or, as Tywin said in Storm of Swords, "When your enemies defy you, you must serve them steel and fire. When they go to their knees, however, you must help them back to their feet. Elsewise no man will ever bend the knee to you." This isn't some "stupid stark honor" thing. Rulers like Tywin, Stannis, Robert, and even Aegon the Conqueror often pardoned people who fought against them on the condition that they swear oaths of fealty. Just like Jon did... And that's in normal times, let alone a time when unity is imperative because a giant army of zombies is coming to wipe everyone out.
If Jon had stripped the umbers and karstarcks of their lands, he would have ensured their emnity. Instead, he probably swelled the ranks of his army by a couple thousand soldiers.
Anyway, Sansa was right in saying that allies should be rewarded. So here's a compromise that could have worked: after forgiving the remaining umbers and karstarcks and allowing them to keep their ancestral homes, Jon could have arranged the karstarck girl's betrothal to one of his allies, arranged for the umber boy to be fostered with one of his allies, and given the Dreadfort to one of his allies (since house Bolton is now extinct). That way, he could reward his loyal vassals without making enemies of anyone.
But like I said, Sansa pissed all over anything like that.
