Yes, such acts are. I cannot speak for the city of Brunswick or the state of Georgia, but they have a pretty good idea what to expect from the anti G-8 mob. I suspect that it was seen as a 'sit here and take it or do something about it' situation. A better response might have been to rustle up every cop they can get their hands on to be in town and quietly inform the protest organisers that nonsense will not be tolerated.
If your city is going to host a G-8 event, police pay and overtime are part of the cost of doing such business. If I scheduled events for the G-8, I'd lean towards holding them on cruise ships, where the security situation is more easily managed.