To be fair, you cannot really open a door of an airplane mid-flight (due to pressure difference), so passengers were in fact in much less danger than they perceived.
This is true when the aircraft is at altitude, but there have been cases of passengers opening doors in flight at low altitude, where there is little or no pressure differential:
Yeah, the door opens in before it cams over to opening out (or can be thrown out onto the wing in some cases), so it’s being held in place by about 3000 kilos of force at typical cabin pressures. Good luck trying to pull it open.
Now, near the ground before the aircraft is pressurised, it could be dangerous mostly because it could pose a risk to the aircraft structure or systems if it tears off and impacts the aircraft in flight. Other than that, a jetliner can fly perfectly well with a door open at low altitude. (Not sure about special large cargo doors though)
https://news.sky.com/story/amp/passenger-arrested-after-plan...