It is completely illogical. If I, you, and seven billion other people rooted for Kansas City and they ended up losing to the Detriot, it would not have affected the outcome of the game. No one would have any tangible effect on Dallas benefitting with the Chiefs winning the game.
My apologies but I have had this discussion with people since my 20's. This is a total self-made fallacy. Dallas is in control of its own fate. If other teams' wins, loses and even ties benefit or hurt Dallas' playoff seeding or berth, it is fate. People are trying to control fate. That is impossible.
Just makes zero sense that some people object with other people telling them rooting impacts nothing in the real world EXCEPT them emotionally. It is the truth. Why must truth be dismissed because it does not fit within the parameters of an uncontrollable narrative?
/rant