I think this example doesn't match the point being argued. You assume the implied rudeness to mean that arguing parties insult each other - but insults are just on one end of the spectrum of "rudeness".
If you argue on the premise that rudeness is the disregard for the opposing party's feelings, there's plenty of opportunities for rational arguments that will provoke a very emotional reaction and thus be discarded without further scrutiny.
So, I'd argue that while the premise that some direct and blunt statements can be rude, that doesn't mean that any rudeness (esp. insults) is a better argument.
So, I'd argue that while the premise that some direct and blunt statements can be rude, that doesn't mean that any rudeness (esp. insults) is a better argument.