Why should someone else's decision to watch a movie affect my decision to look out the window?

In practice, I haven't been on a flight in many years where this has actually been an issue. I never use the IFE myself, but even in coach on UA the little seatback screens don't seem like they'd be affected by an open shade. But if it was really causing a problem on my seatmate's screen, I'd close the window. I've done that before to help out a guy using a laptop in a seat next to mine...I just had to wait a few minutes until the sun's position relative to the plane was different and then I reopened the shade.

Ummmm...huh? Passenger airliners have always had windows, long before the concept of security around airports and airplanes existed. I'm going to guess that they were originally put there for sightseeing. It would certainly be easier and cheaper to build a fuselage without them.

In later years when the plastic windowshades we know today were added, someone determined that they should remain open at takeout/landing for safety reasons. Although some airlines don't mention or enforce this, at least there's some logic behind it.

I can honestly say I've never heard anyone try to connect the windowshade issue to security for a normal commercial airline flight carrying civilian passengers, which is clearly what we're talking about here.