There was a law that started literally that day that prohibited dancing at the Jefferson Memorial. It was the result of a flashmob that some lady started there, that ended up disturbing the peace, and they had to arrest her. So basically they outlawed it there, to keep dumb **** like that happening there.
So basically, these people felt it was a fantastic idea to get a bunch of them together, on the one day that the police would be there to stop protests of that nature, and start breaking the law that just came into effect that day. If that's the video I think it is (just clicked on it to see the name of it), what you see is AFTER the police gave everyone multiple warnings to clear the area.
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