There is no arc of history. That quote by Martin Luther King Jr., although it sounds nice, makes us complacent. What is implicit in that statement is that no matter what we do, things are going to be O.K. in the end.
The truth is that there is no single line of history. History is really up to individual actions. It is important to assert what we care about, especially when the circumstances around you change. When the incentives around you change, whether it is a new government or a new boss, it is important to recognize that it is human nature to adjust, to adapt, to fall in line, as that Milgram experiment at Yale revealed.
The little actions, the little affirmations, do matter. They reveal who you really are. In so far as things bend, it is because we bend them.