That video doesn't prove anything and doesn't demonstrate the long term effects of water on a circuit board over time. Dropping the board alone in the water then allowing it to dry before using it for a minute is not at all like having the gun on and working before diving into a puddle and expecting it to continue working. It's not the water that kills the board, it's the conductivity that allows the board to fry itself with its own electricity. If he'd dunked the gun in the water while it was on, it would have been a different story. That also doesn't account for possible long term effects: fading display and failing components.
For the OP, it's certainly safe to play in the rain with an electro, so long as you keep from falling into any puddles. For the future, there are two basic precautions you can take. First is to take off the grips and wrap saran wrap around the frame before putting the grips back on to reduce the chance of any water hitting the board. The second is to cover the porting (if any) on your barrel. This is to keep water from getting inside your barrel and throwing off accuracy.