That reminds me of a conversation I had at the Yushy Jin Yong Forum a few years ago (when you've been discussing wuxia on forums as long as I have, you meet quite a few interesting characters and have quite a few interesting anecdotes to tell, for better or worse).
On that occassion, the topic was the Juchen Jin Empire that was the collective antagonist of LEGEND OF THE CONDOR HEROES. I made an offhand remark that the Jin people were Tartars, a term which some historians have applied to the Juchen and other steppe peoples. Anyway, this guy latched onto the idea that the Tartars were one specific group of people from one specific time and place, and that the Juchen were a completely different group. Point taken, and he was right about that. Although some historians have indeed called the Juchen "Tartars," strictly speaking, that's not correct. I pointed out, however, that "Tartars" is a term that has been used to refer to various steppe peoples scattered across Eurasia and did not refer to one specfic ethnic group tied into a specific location or time period. That guy wouldn't take no for an answer.
He kept on hounding me and hounding me and hounding me
on this point for a week until I *finally* (just to get him off my back) agreed with him (at least verbally) that the Tartars referred to just one specific group of people at one specific time, and didn't include any other groups such as the Uighurs, Khitan, Mongols, Huns, etc.
Then the guy disappeared from the forum and never showed up again.