What are the consequences of disobeying cabin crew during emergency?
There are laws which mean you must comply with crew orders at any time whilst on an aircraft. This is especially important in an emergency. In the Singapore example, imagine if a passenger had, without thinking (as tends to happen in emergencies), opened up a door on the side that was on fire. Fire could have entered the cabin, ensuring fatalities. 

However, no prosecutor is going to pursue charges against someone for disobeying directions in an emergency, unless their actions clearly led to serious harm. Every evacuation, so many people stop and try to get their carry-on items, when they are clearly told not to. Even though this increases the chances of other people dying, nobody has been prosecuted for that (to the best of my knowledge).