Well, my argument would be that he was the Holy Roman Emperor, but for some reason people argue that his empire still wasn't the Holy Roman Empire, but a Carolingian/Frankish Empire.
EDIT: I have a similar problem when people refer to the medieval and Renaissance Roman Empire as the Byzantine Empire.
[rant]The citizens of the Empire referred to themselves as Romans, but historians call them something different! What? Remember the joke about the HRE? They weren't Holy, they weren't Roman, and they weren't an Empire. But we still refer to them as what they called themselves, the Holy Roman Empire. But we don't for the Romans? Ugh.[/rant]
EDIT2: I know I probably annoyed a ton of history geeks and historians with my rant.