If you knew how old I was when I first heard these stories, you would freak out twice. Once to find out how old I really am (im not so sure Im going to share with you the science on that) and the second time at the idea that this is the kind of story people tell children in the east (although I have heard these stories told in the west too, by school teachers to classrooms of students, so quit being such false prudes)
When the Mongols asked the northern people why they hadnt ran to the south to get out of their way they told them about the toilet issues. I guess the Mongols decided that "my country right or wrong" was a better way of thinking than "Fuckin Christ Man dont use me like that". Being a less fastidious sort, not as inclined towards pottery we get the classic apearance of feudal chinese coiferry thanks to the Mongols.
Actually, when people first heard of running toilets they thought they were only doing it to the young petty elites who hadnt studied well enough for their exams, but you know how cheating goes, one cheat gets in and doesnt want to be found out so he lets other cheats in, but then people dont realize the nonpartiality of chinese hypnotists, or how confusing it gets when wandering around in the dark you do your buiness in a high ranking official, then you realize you cant even tell which one it was. After a while people start to view everyone at court as toilets. People realize the whole shebang is dispicable and start opting out. But then when encountering a forign army that views you all as a bunch of pansys, its hard to make clear which one is being a ninny and which one has comendable qualities.