Prior to 9/11, hijackers weren't resisted... tactics changed after that. Active defense is now a reasonable strategy.

During the cold war drones were huge, noisy, expensive, and had relatively short endurance. They weren't used in waves like drones can be now.

Zone denial seems like a reasonable response to today's threat environment.

To clarify, I am pretty sure they are talking about flybys by actual manned fighters.

But it's a fair point that shooting down an unmanned drone is a lot less aggressive than shooting down a manned one.

Of course, not starting a war with aliens that don't shoot seems wise.

you miss the point - it isn't Florida with the "stand your ground", it is international waters where one side's "reasonable" most probably means absolutely nothing to the other side(s). You shoot at something in your denial zone - it is an act of war, and you open yourself to reciprocation. China, for example tries to establish various zones in international waters for the reasons of its national security - the US ships and planes still sail and fly right through rightfully without giving a flying f-k.