I really want to believe that a single switch doesn't control whether people in the back of the plane can breather or not...
Really though there are plenty of switches in any cockpit that will result in the death of all aboard if no corrective action is taken.
Do you freak out about driving? Plenty of controls in your car you could say the same thing about. Yanking the ebrake at highway speeds in rush hour traffic isn't gonna end well.
Edit the 5th or so: There are also times when the pilot will legitimately and safely depressurize in flight, like when descending to the one of the super-high airports that are actually at higher altitude than typical cabin atmosphere, like La Paz Bolivia (over 13000ft, compared to a typical cabin altitude of 5-8000 or so. They do it gradually while descending, so they don't make everyones ears go bang all at once.
Edit the 6th: Also, there's a big difference between turning off bleed air (which is pretty benign) and actually hitting the emergency pressure dump control, which is protected by a guard that holds the switch in the normal/auto position.
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.
Must have been quite distressing.
The idea is to keep everyone except the pilot alive but unconscious until things improve. I think it's preferable to everyone unconscious and eventually dead.
If both passengers and the pilot aren't being supplied with enough oxygen to remain conscious 100% of the time, then something has gone horribly wrong. If the reason passengers aren't being supplied with enough oxygen to remain conscious is because the pilot cut off their air supply intentionally, then that's even worse. (Though again, thankfully that situation seems to be extremely rare.)
Wait, is there an emergency pressure dump control?
I kind of just assumed turning off bleed air would be the only option, and I would have assumed that turning off bleed air would complete depressurisation within a few min.
Here’s what it looks like on a 737: http://www.b737.org.uk/images/cpcspanel.jpg
The switch is the guarded toggle a bit left of center on the bottom, next to the two round gauges.
Now pilots would hear the warning, scan the indicators and see the indicator, and are trained to put on their oxygen masks immediately. The cabin masks would deploy automatically. Then they follow the checklist which is to descend to a safe level if the pressure is uncontrollable (which it wouldn't be if it's just switched off).
It's very unlikely the pilot would turn off cabin pressurisation, but it would be pretty gentle and warning alarms and indicators would start pretty quickly (including on EICAS on newer planes like the 777). The pilots could easily fix it well before their or the passengers' oxygen ran out.
A few of them crashed after very long flights, on approach of the runway. Inexplicably, they suddenly felt right when they should have deployed landing gears.
So aircraft makers learned from that incident that no amount of training can mitigate a bad user interface. Especially if the user of your interface is dead tired after a 12h flight.
(E.g., fuel selector switches that can enter an unexpected state while looking like they're in the correct state, take-off/go-around switches that could be triggered by a first officer wearing a watch reaching for the speed brake lever, attitude indicators with ambiguous backgrounds, three-pointer/drum-pointer/counter-pointer altimeters)
Do you realize you're entrusting two people in the front of the plane with your life as soon as the plane takes off? There are probably DOZENS of switches that if they are flipped maliciously will result in everyone on the plane dying.