Are they trying to 'turn them in' for something? The last I heard, it was legal to peaceably assemble and petition the government for a redress of grievances.
No, not at all. You're correct; it is legal for them to assemble. It's in the interest of truth; if you get your news from the mainstream media, you hear nothing of this. It is a pity our media no longer even makes a pretense of objectivity. An objective media is a prerequisite of a free society.