Mmmm not quite how I meant it. If we war someone, clearly we're looking for a fight. If the opposition are douches or dirty, it will cause a grudge. If they don't make themselves stand out like that, we'll more or less forget them.
When whole kingdoms participate in flame wars, guaranteed it will turn into a grudge. Guess it's up to the monarchs to reign in their nubs before it gets out of hand.