I think the PO might have been correct

Follow the link here and watch the video. While the police officer did not express himself correctly, the guy protesting is wrong. You can not put up any old sign you want on public property. On your own property sure. Now if this was at a protest and the police officer only singled him out. That was wrong. All protesters should have been told to put down their signs.

Can't tell from the video. Why don't you watch and tell me what you think?