The person in the window seat usually has control over whether the window shade is open or closed. However courtesy plays a role too. On overnight flights across time zones window shades should be closed whenever possible – many passengers are trying to sleep, but it may be light out early. The outside light might also interfere with an aisle seat passenger seeing their laptop screen and getting work done.
Reasonable requests should be accommodated, though it’s up to the passenger in the window to make the trade-off decision. One key to peace on board is good communication. “I’d love to leave the window shade up just as we take off, and I’ll be glad to put it down once we reach cruising altitude” is hard to argue with.
These passengers, though, couldn’t come to a reasonable understanding.
Takeoff and landing are the most critical parts of the flight. Window shades should be open. Passengers have greater situational awareness, and everyone’s eyes are better acclimated in case anything does happen. Supposedly the incident occurred on descent, after crew had announced that window shades should be open. That may make you think the passenger raising the shade was in the right here. I disagree.
It’s up to the cabin crew to enforce their instructions, not other passengers. At most the passenger raising the shade should have consulted with crew who would have acted as they deemed necessary. Never take a dispute with another passenger into your own hands unless your safety is at direct and immediate risk. Neither passenger was right here.
Some modern aircraft – like the Boeing 787 – allow crew to manage these things themselves. While passengers can electronically open and close shades, crew can lock them. That would have been a great feature here!