I think the real problem with this thread is the generalization. It seems very obvious to me that in both ultra racing and marathon racing and even 10k racing there are both those who run and those who walk.
Now, who gets to call themselves a runner is a better question. Clearly the lines are not defined by race. The are certainly ultra, marathon, and 10k 'runners' out there. There are also ultra, marathon, and 10k 'walkers', 'joggers', and 'mixed-breeds' out there.
Obviously the solution is to treat this like race. If you are half Mexican half Canadian you say you are Mexican-Canadian. So if you Walk/Jog a race you are a Walk-Jogger.
Now, also important is the percentage. If you are 75% Irish but have that one German Grandma, you better tell all the world that you are 75% Irish, 25% German, lest you play them for fools regarding your true heritage.
So yeah, I consider myself to be a marathon '89% Runner, 9% Jogger, 1% Sprinter, .5% Aid Station Grabber, .5% Crapper'. But I most associate myself with my crapper identity so that's me now. I crapped my last marathon. Big marathon crapper over here.
I am thinking that OP has a personal experience with an individual who has run parts of an ultra at a pace unworthy of the 'runner' race (likely a mixed breed of sorts). Because clearly the problem is not specific to ultra marathons. It also sems a bit 'runner' supremacist to be making specific claims of which paces are included in the 'runner' race. My guess is OP can't run ultra marathons himself, as the fact this thread exists points to the fact that OP is a little bit insecure about his own place in the 'runner' race.