You know, something that is bothering me about both sides of this argument is the failure to acknowledge that there are people who do ultras because it's on their life list, and that this reason is perfectly valid.
Why is the pursuit of excellence the only thing that matters? Is my wife not allowed to enter a marathon because it will take her 4 hours? I'm a middle distance guy, but in a few years I'd like to run a marathon or two: a fast qualifier and then Boston, just because it is what it is. I have no desire to run more than that (maybe a third, just to try to max out my PR), but maybe I'll end up running 10 like my high school coach did; after his first he said he was through with them. I am also into rock climbing, and I'd like to do something on El Capitan in Yosemite because you know what? I scrambled up the base of the Nose a little ways and I was INSPIRED.
This life list/achievement vs. busting our balls for the love of sport thing is a conversation the climbing community has all the time. Do we really want a whole bunch of gumbys running around with their brand new, matching gear that they don't know how to use, littering all over our favorite crags once or twice a summer? The reality is, yes we do. We want them because more participation overall creates more opportunities for dedicated competitors like us, and provides incentive for companies to make more and better gear for us. This rising tide LIFTS all boats.
You can make the case that we will produce fewer elite runners if the public perception is that all races are about finishing. I would argue, however, that the more people we have involved, the more kids who are going to see it as an activity they can participate in. I would also argue that if this is the concern of the competitive running community, then it is our responsibility to cajole and hagle that "I have to try my best, even if I suck" mentality into the popular consciousness. How many fun runners do you think work at Runners World, anyway?
And as models for virtue go, let's not forget that Aristotle also thought heavier objects always fall faster than lighter objects and that the sun goes around the earth in a perfect circle on a crystalline sphere. He was sophisticated for his time, but he is a country bumpkin by any modern standard.