The First Amendment (Amendment I) to the United States Constitution prohibits the making of any law - interfering with the right to peaceably assemble or prohibiting the petitioning for a governmental redress of grievances.
What did these officers not understand when they took the oath... but, since they wouldn't and didn't read the laws pertaining to these protesters I guess it is too much to ask. I saw no reason in the video that the LEO's could not have been reasonable but they have to be bullies, press their own erroneous interpretations of the law, and assault a citizen. Are civilian overseers not aware of these incidents or are they afraid of the police as well?
The average person is not going to understand that their rights have been eliminated until authority forcefully man-handles them, pushes them in a direction or to a place they don't want to go, and beats and violates their loved ones, all while under the color of law. But, since history isn't taught anymore references to 1930's Germany probably doesn't resonate in the least...