There was for several decades--decades in which we saw perhaps the most progressive action on civil liberties--a very real and immediate threat of domestic terrorism from factions who felt oppressed.
At the end of the day, having ceded the monopoly of violence to the government, it becomes very difficult to merely ask nicely to have your freedoms restored. More Malcom X's would probably have helped the Occupy movement, least of all because the "We are oppressed, we're starting to fight back" is a narrative familiar enough to the American psyche.
I think the threat went beyond domestic terrorism; it was bordering on armed revolt and revolution.
We don't need that now (and it would be hopeless vs. modern police/military unless you had an issue, like 2A, supported by most of the individuals in police/military, combined with a constitutional justification like an unambiguously unconstitutional move by one branch of government vs. the others, like a hypothetical future President closing the Supreme Court), but a similarly forceful threat, like removing $100b/yr of business from the US or a mass expatriation, could probably work.