Overwhelmingly the most common case is people accusing others of posting in bad faith merely because the other's view is so far from their own that they can't conceive of them having it for legit reasons. This is a reflexive reaction—a feeling that we all need to recognize and stop ourselves from expressing in raw form. When people vent it into comments, the result is either war between the two sides, or, if one side outnumbers the other, an ugly mob dynamic in which a few people are ganged up on for being different. Those few either leave, or they become resentful and break the site guidelines badly themselves, as a way of lashing back against unfair treatment. All these outcomes poison the community.
Not to pick on you personally—it happens because of how human nature reacts to the weird conditions of the internet, which we're not wired for. It is hard for all of us to grasp how large and diverse the community is, and how divided it is on divisive topics. Nationalistic themes are some of the most divisive ones, and unfortunately are growing more common these days.
If we go by the data we actually see, the phenomenon itself is vanishingly rare. Why is there so much commentary then? I can think of two explanations: either the foreign spies are cleverer than we are, or there is something in how human nature meets the internet under current social conditions that is leading to mass projection. And of course it could be both—but how are any claims about the former falsifiable?