This one of my favorite observations on the subject:

Why People Support Rotten Empires

It’s nice to think that a government that Goes Too Far will eventually cause the citizens to rise in righteous wrath and throw the rascals out. It’s also convenient when all the defenders of the Evil Empire wear uniforms (except for the occasional Secret Police spy). Unfortunately, we know from centuries of experience that it doesn’t really work this way. The worst tyrannies imaginable have been enthusiastically supported by people no worse than you or me.

Without going deeply into psychology, here are some of the reasons why citizens support tyrannies. You can use these to make your fictional Evil Empire and its people something more than laser fodder.

Citizens fear that the unknown will be worse than the known: a foreign philosophy, a strange religion, or perhaps society breaking down to anarchy. They may fear and hate an enemy population, especially if they are a different religion or race, let alone species: Do you hate the Bug soldiers because they are cruel and ruthless, or because bugs are icky? Many people fear that a new government would cost them their jobs or personal power; in a corrupt regime, they may have good reason to be afraid of justice. A clever regime’s propaganda will play on all these fears, constantly portraying the foe as inhuman, the rebels as terrorist killers.

People who are used to obeying the law often have a hard time changing their habits when the law becomes oppressive. They still believe that “the police only arrest criminals; honest people have nothing to fear.” When the rebels break into an armory to get guns, these people see only that a robbery was committed. Enough of this and patriotic citizens may volunteer for the army to fight the wicked rebels. Obviously, rebellions find more support on worlds that were free until the empire conquered them. But even there, some citizens may hate the occupier but doubt the rebels would be any better. You can fight for “freedom” – but once you win, you have to set up a government.

And people may be loyal to the idea, or to the ideals, of a nation or empire, even when the reality is tarnished. “My country, right or wrong . . .”

It is not evil, or even cowardly, to be afraid of starvation, torture, and death. Any successful rebellion must overcome these fears . . . to convince the people that anything is better than slavery. Meanwhile, the government is telling them that anything is better than anarchy. Which is why rebellions have a hard time of it.

– John M. Ford

@Jay Bryant There is certainly some truth in what Ford says.

But there are also the people who hid Jewish families like Anne Frank's during WW2, even though they were not personally under attack by their government. Sam goes for the entire nation of Denmark who collectively worked to rescue their Jewish population.

And then there are the hundreds of peaceful Indian protesters of India who were slaughtered at the Jallianwala Bagh massacre by British troops. This led to the non-cooperation movement of 1919-1922 headed by Mohandas Gandhi.

In 1965 in the US there was "Bloody Sunday" at the Edmund Pettus Bridge where 600 people peacefully marched for their civil rights and were set upon by white enforcement officers who tear-gassed and beat the protestors. Subsequently, these people continued their peaceful campaign for the right to vote.

In 1976 thousands of black South African children in Soweto peacefully protested the law that mandated the teaching of classes in Afrikaans. When the police responded with violence killing 176 people and injuring 1000 more, the international community was appalled. This began many countries, including the US, divesting from South Africa. This was an important moment in the eventual ending of Apartheid.

John Ford seems to be speaking about the behaviour of the privileged classes under tyrannical governments.