How old is the kid? Have you just tried asking them why they are arguing or asking how they are feeling at that moment and then helping them to explore those feelings and why they are feeling them?

Maybe they see what you are saying is unfair, and if they do, maybe try to explain it from the point of view of an adult. Depending on the age, it could just be a super young kid doing what young kids do, i.e., pushing boundaries, or it could be any number of issues. I think teaching kids to be as emotionally aware as possible is a good thing, though.