The camera man was a bit distracted by the spark on the high voltage generator and it would have been nice to see where the magnet on a stick was with respect to the beam of electrons. However this demonstration does show that the beam bent downwards when the magnet was behind the screen and upwards when the magnet was in front of the screen. So, reversing the direction of the magnetic field reversed the direction of the force on the electrons. Therefore the electrons interact with the magnetic field as though they are charged particles. The particle nature of matter!