Well, based on that, I would call it a race. NASCAR has defense and teams, to an extent. Cycling does, too.
Alright...I just looked up the wikipedia article on it, to get an idea of the rules, and it's definately a sport by my guidelines.
From what I read, you get points based on your lead "jammer" lapping everyone, and those points determine the winner. Because there's not a defined distance or a time limit in which you see how far you can get, it wouldn't be a race. You're not, for example, seeing which team can get a player around the track 40 times, or something.
So, I hope that makes sense as to why it would be classified as a sport and not a race. Luckily I have free time this week. Not looking forward to getting back to the grind next week.