Having been at the front of the protest movement back in the 1960s, what always amazed me was how easily we won our various confrontations with authority. I went along because it was the thing to do, got to meet girls, could exhibit my morality in a public place and did mildly care about the issues. But over time the realisation grew that it was absolutely riskless. Nothing would ever happen to me as long as I just stayed in the pack. A few of my friends got busted occasionally but they were the loud mouths who drew attention to themselves. And they would be duly carted off and then join us in the morning for a coffee and a smoke.
I actually saw this demo pictured here as they wandered down Bourke Street after their festivities were over. The answer. Put a couple away for a month or two, the really violent ones, make it clear that there actually are risks to one’s health and safety from going beyond peaceful protest, and it will stop. The major idiots will still keep it up but we minor idiots will wander off and find something else to do.