Doesn't the US have an amendment that allows for this kinda thing?

I am physically sickened by what I am seeing in this video, I know many of the readers of my blog are Americans and I would ask you to please spread this far and wide and complain to your representatives about this disgusting act of authoritarianism. Police officers assaulting and arresting people for dancing without being able to state what crime they are commiting or what they are breaking is is illegal. I thought america was the land of the free.