this is one of those situations where it may not be technically "against the rules", but they should penalize or disqualify him regardless. cant just be a dick like that and get away with it, or else people will start trying to pull all kinds of other stunts that "arent against the rules". it sets a bad precedent to let shitty sportsmanship like this go unpunished. if anything give him a 30 second penalty or something.
at any rate, if i were behind him in the race, id be waiting for that dude in the parking lot after the race. not even kidding.