One Way to Halt a Person that You Know from Participating In Collective Destruction (AKA, Rioting)

 I heard this from a colleague once. What you do is go up to that person (providing that it's safe), look them straight in the eye and simply say their name, Rodney, Jason, whatever it may be, because when you do that it sometimes jolts them back into believing that they're a unique human being and not merely an idiotic appendage to some undifferentiated mass. No, you may not succeed every time but, hey, it's better than standing around, recording it on your cellphone, etc..