Then you take them aside, arrest them, and deal with them. Cut the head of the snake off, so to speak. Without their communist mob 'leaders' they tend to dissolve and lose their gumption very quickly.
The trouble is they know who the leaders are. However, they do not bother to arrest them, because the government is stacked with folks who did the same thing not long ago. They just arrest small potatoes, while ring-leaders go on to stir trouble in yet another riot or rally, somewhere.
They are overstaying their welcome. Sympathetic attitude for these losers are souring. Erstwhile Roh's supporters now want to see them locked up, while those in power would rather not. They may feel now that their time could be running out, even though they try hard to shake off such apprehension.