What leaving does is control how far the pendulum swings. Imagine if Fermi hadn't left Italy? Or consider Lise Meitner who didn't leave Germany when everyone else did (http://en.wikipedia.org/wiki/Lise_Meitner). In her words, "It was not only stupid but also very wrong that I did not leave at once."
The part you're conveniently forgetting is at what cost?
Sure, the pendulum may swing back the other way eventually but how many lives are going to be destroyed during these unnecessary oscillations.
In this case, the pendulum can remain autocratic far longer than your life is worth it - if you feel that fighting is not possible, perhaps the best move is to worry about your own (family's) safety first.
I think that is a great metaphor here. If the government no longer respects the people, then the right approach is to stand tall and say things loudly. If they do then compliance is better.
Edit: Also, moving when you have family (partner, kids), becomes even more complex and stressful. It's simply not a viable option for many.