I lived in D. C. during the Viet Nam protests in 1970 when not, hundreds, but thousands of protestors were herded into JGK Stadium. Why? The protesters were trying to shut down the government. They didn't but they tried. I walked to my office from Georgetown and saw protesters who had rented Ryder and Hertz trucks, and were sweeping broken glass into the streets to disrupt traffic. Cars were turned over and set afire.
I believe people should be able to protest peacefully. Protests of the type I saw in Washington went well beyond that though.