The issue isn't to get everybody or even a majority of the population to act, 10% would be enough. 30 million people marching from all over the country on DC to converge on the lawn of the White House would force the government to give in to their protests; 30 million people is far too many to remove using riot police and even you are prepared to shoot at them do they wouldn't have enough bullets to get them all (or even a significant chunk).

The problem is that you have to get 30 million people to act at the same time, together. I can't see anything but a massive draft that would galvernize that many people around one course.