Sealear, even the most inept union would have managed to stop Emirates pulling half the tricks it has got away with over the last few years. Remember, they don't even have to follow the labour law of their own country. The only limit to the degradation of our terms and conditions is the fact that they need to recruit new people.
Leaving isn't as simple as you make it sound. It has been said before but it is huge disruption to move your family half way around the World to come here and probably an even bigger disruption to move them back again. It is certainly not the same as getting a new job with a different airline in the same country and, respectfully, unless you have tried it you don't know what you are talking about. I'm sure disruption to childrens' schooling is a major reason many don't leave.