Well yes futile in as much as it wont get their goal, but sometimes it is better for people to let off steam. However, like I said above obstructing others going about their business, causing disruption to business, vandalism and violence are across the line.
I would have though burning the countries flag was a stupid thing. That will be there for future employers to see for many years. It can only come back to haunt you. It could also be seen as an act to incite violence I would have thought?