Dojos, dance schools, even graphic art schools are like families. The new student - especially the gifted one - often has to deal with the jealousy of the senior students. Conflicts and rivalries can turn ugly if the instructor in charge is not careful to avoid inflating some student's ego, and to hurt a previously best student by suddenly relegating them to second place.
Or it may just be that the guy was born jealous genes, period. Some people are like that.
Anyway, I agree with Michael and Keith. The world is not perfect, and if you are doing so well in the dojo, just let him marinate in his own problems and move on with your training and your life.