It would be one thing if the light you "owned" were confined to your personal space - but it's not. It's spread across the cabin.

I see keeping your window shade open during a flight as akin to playing loud music at home with your windows open. Sure, you're allowed to do this. But it's highly inconsiderate and anti-social; it disturbs everyone else and interferes with their ability to enjoy the service that they've paid for.

Just my two cents.