I don't see why having a judge rules something out of being a sport. team games have referres/umpires whose judgement on the rules may change the result of the match, yet any definition that rules football or cricket out of being a sport is obviously too narrow. Once you allow a referee how can you exclude a judge?

I reckon its a sport if its competitive, physical (no chess or card games), raises your heart rate (sorry, no darts or snooker) and isn't for a useful purpose (no digging the garden). Motor racing counts because anyone who thinks its not hard work slinging a car or bike round a track is wrong. Mick Doohan used to have a resting heart rate way down in the low 50s IIRC.

Come to think of it, scratch competitive, because mountaineering is certainly a sport.