These rules mostly exist not because there is a grand plan to stifle discussion, but because time and time again you see these sort of arguments devolve into low quality material that takes over the entire space.
I don't have a problem with the rule. I have a problem with it not being part of the guidelines. Besides, I've seen threads labeled "flamebait" that have more and better discussion than the main thread. That's not how it's supposed to work.
That prompted me to read the guidelines for the first time, and I'm seeing multiple relevant rules, such as asking not to fulminate, eschewing flamebait, avoiding ideological battlegrounds etc.
I've been warned for this for stating and sourcing true facts from fairly unbiased sources, while this person calls the entire country of Japan "psychotically fascist" and nothing happens? What's wrong with this picture?