How much evil throughout history could have been avoided had...

How much evil throughout history could have been avoided had people exercised their moral acuity with convictional courage and said to the powers that be, 'No, I will not. This is wrong, and I don't care if you fire me, shoot me, pass me over for promotion, or call my mother, I will not participate in this unsavory activity.' Wouldn't world history be rewritten if just a few people had actually acted like individual free agents rather than mindless lemmings?