You don't think it takes a pretty drastically different set of morals to back Dijkstra, and thus the North, versus Roche, and thus Nilfgaard? Or to empathize with the Bloody Baron versus condemning him? Or to support Hjalmar versus Cerys versus Svanrige, and the different forms of government for Skellige that they represent?

As for "the canon obsession," I don't think it's unreasonable to want a definitive answer to the question "what really happened during this story?" when story is such a massive component. Imagine if a movie was released, and some theaters got one version of the film in which the hero saves the day and returns home victorious, while some other theaters got a version of the film that was 90% the same and was marketed as the same product, but in the last 10% the hero is defeated by the villain. Would it be unreasonable to ask "well which version was real?" Especially if further stories were going to be told in that universe? When the story is the product, and when further stories (and therefore products) are going to be told/sold as continuations/adaptations/sequels/whatever-you-want-to-call-it of the first, canon is an important thing to be able to definitively know.

A good way of handling this is, I think, the way Bethesda handles canon for the Elder Scrolls. Take Skyrim for example, where a single character has the opportunity to join both the Companions - a noble group of warriors who fight for the downtrodden - and the Dark Brotherhood - a shadowy group of assassins who work to sow darkness and chaos. It would be incongruous without some serious mental gymnastics to say that the canonical Dragonborn saw both of those questlines to completion. However, to invalidate one or the other from official canon diminishes and cheapens the experience of players who loved the questline that was invalidated. What Bethesda does, therefore, is to say that the canonical Dragonborn did the main quest line, and that's it. They also say that for every side quest and quest line in the game, those quests were completed during the appropriate time frame, but not necessarily by the Dragonborn. They were done by someone, who may or may not have been the Dragonborn, but who did them is lost to time. That way, every eventuality is canon, but whether or not certain side quests were done by the Dragonborn or just by someone else at around the same time doesn't matter.