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.
Also, thanks for all the hard work here on HN. I know it's not a glamorous job, but yall are doing a great job handling all this. You work hard and it shows.