re: Serious question concerning shooting at a moving target (vid link added)

It's all about relative speed. If they are travelling faster than you it would be like you were standing still aiming at a target moving away from you at whatever the speed difference, slower would be like them moving toward you at the speed difference and zero speed differential would be like shooting at a stationary target.

Of course it would probably be like shooting from a bouncing vibrating platform if you on the helicopter.

ETA: Didn't watch the video so I made an improper assumption. Now it becomes about relative velocity (speed and direction) rather than simply speed, the crosswind analogy is pretty good, as the bullet already has the speed of the helicopter imparted onto it, so you would had to lead to account for the crosswind effect if the car and chopper are travelling at the same speed. If not you have to account for speed differential and take the crosswind effect into account.