i noticed the same thing reading this thread, the guy who started it was probly just determined to get someone to agree with him so he made a new login ID. anyways, you are never going to be able to prove that running (nor any other of the less popular sports) is not a sport. but here are my thoughts:
having run XC and track competitively the past two years, and knowing many hardcore swimmers, i can attest to the fact that running falls into the category of a fitness sport. swimming, biking, and "racewalking"...whoever does that, are all part of this category.
it is not inherently fun (although, like anything, it is fun when you are one of the best at it), there is no ball, no goal, nor a way to score points. it takes comparitively little technique, practice, or strategy, and depends heavily on natural athletic ability. it is not a true team sport, but exists in highschool and college athletics anyways. because of these characteristics, it will never be as popular as what the general population considers the "real" sports: football, baseball, soccer, basketball, and hockey (if it ever comes back)