So, we are all in agreement:I wouldn't but those are entirely different circumstances, just as the Saudi incident was. No smoke or flames in the cabin in this incident, and no other evident immediate danger to the passengers. Had this incident really been an actual fire, what the passenger did would most likely have made the situation more dangerous.
1) There are situations in which a passenger >should< open the emergency exit on their own, without crewmember instructions.
2) This should only be done when absolutely required and when it is safe to do so. In this case, the passenger was wrong to believe the conditions had been met.
What caused the error? Lack of training? Lack of good judgement? Lack of the experience required to execute good judgement? I don't know. But it sounds like the passenger believed he was acting properly. I suspect a lot of attention will be paid to the steps taken by the crew to set conditions that help reduce the chances of this sort of thing (provide information and direction to passengers promptly, monitor door status immediately and continually in the case of a rapid stop or other unusual occurances, have the FAs get to a position to monitor the exit rows as soon as it is safe etc).