A just person must live within his moral belief system and act responsibly to it in the world. A decision to act against the potential rights of a driver who may be guilty of nothing but has been reported by another to have done something that could be a danger to himself or others if continued is not going to be weighed not by grand theoretical concepts of personal liberty but whether the person can live with a bad decision. If a person can live with the consequences of inaction based on a theory of noninterference, if the person identified later kills himself or others as the caller had feared, then he or she may actually do nothing, but if a person couldn't live with that possibility they will make a stop. Such a determination will always be a judgment call based on ones internal ethics and gut instinct regarding the seriousness and sincerity of the report, in my opinion.