What People Can Become Accustomed To

Doing research on protests in India for work over the last several weeks (while also happening to be watching Mad Men - not at work, just in general over the summer) it's really struck me how variable the standards on acceptable police behavior are.  In my country, events like the Chicago riots and the Kent State shootings were huge cultural moments that shocked the nation, sparked widespread condemnation and self-reflection, and played a pivotal role in mobilizing the anti-war movement.  Meanwhile, in India, similar incidents were almost commonplace.  I've read about literally hundreds of protests on a wide variety of issues which follow the basic script: "demonstrators marched to the square shouted slogans [against caste discrimination, against corruption, for a separate Telangana, a separate Vidarbha, etc...].  When the demonstrators refused to follow police orders to disperse, police threw tear gas grenades and opened fire, killing [2, 4, 7, 15, 30, etc...]."  While these crackdowns do occasionally backfire, sparking demonstrations against them, very often the crackdown passes by with no condemnation and seemingly little notice.

So here's the puzzle: Why do levels of tolerance for police brutality vary so widely across different societies?  Both of these societies were democracies with stated commitments to human rights, protection of their citizens, etc... What are the key difference that lead to "minor" incidents sparking such domestic backlash in the United States while much more "major" incidents in India have little to no effect?

I don't have a good answer (though that would be a really great article) - but a good answer could really help in our understanding of how nonviolent movements mobilize.  Backfire effects have been critical for a lot of nonviolent movements, so predicting when they're likely to occur or not occur could be really key.