That's because none of the opposition leaders are actually threats. They killed plenty of opposition leaders while your parents were alive, though. Martin and Malcom are the two most obvious ones.

But before that, when there was a labor movement, lots of people got killed for being on the wrong side of power.

And finally, the USA doesn't have a USA out there funding and inculcating opposition leaders, connecting them with spies and mercenaries, and building movements to create a coup.