This is a really weird characterization of a normal airplane function.
First, you are seeming to act as if the power between passengers and pilots should be equal. Why would this ever be? The pilot has all the power and the passengers none. Thinking of past hijackings, it's obvious that it must be this way.
Second, the plane needs to be able to handle all sorts of 1 in a million events. Recall there were around 22 million flights in 2021, and of those, exactly 1 was involving a Boeing or Airbus jet (maybe that's even true for Embraer or Bombardier and that tier of airliner). This is because the pilot has a vast amount of controls that are required to handle various events. A plane is a pressurized tube flying thru the sky, of course controls for pressure in the cabin must exist to allow equalization under aberrant circumstances.
Finally, activating this "kill" switch would drop oxygen masks to every passenger in the plane automatically; the pilot does not have any say in this matter. While these masks obviously have limited duration, there isn't exactly a way the pilot could perform this mass murder without their own death or imprisonment being guaranteed too. Frankly, I find your representation of the purpose of the switch so immature as to be offensive.