It was a gated community and the mob broke the gate. They were also trespassing on their private property.
Missouri has a castle doctrine law and the charges will likely be dismissed because of it. They could easily countersue the protestors for breaking the gate in likely small claims court.
Imagine for a second if they didn't do what they did. Do you think those houses would still be standing? Very little happened in this incident. I'd call it a happy ending all things considered.