This is an excellent point and I firmly believe that no one should be rioting.
For subliminal messages, this video is quite suspect:
Disturbed- Land of Confusion
http://www.youtube.com/watch?v=dKFIedvbAik
Though it's a bit old, it shows images that look like a new world order or one world government of sorts (or perhaps the UN?) and shows people rioting, being led by a covered figure.
It seems to encourage rioting and anyone stupid enough to get this "message" would probably do so if they were desperate enough.
Just a heads up on what's out there.