My initial impression is that this is training, not the real thing. The riot is completely confined, the rioters initially ONLY go to the ends of the police lines, and this isn’t a street – it appears to have some sorts of sports markings on it, almost.
But assuming it’s not training, if this explains why the Romans were such bad@$$es, I’m not seeing it. If anything, it looks like a whole lot of restraint on law enforcement’s part. When they’re being attacked by some sort of poles or large sticks – things that could cause serious injury or death – the cops simply retreat once the demonstrators do. They meet active force with strong resistance, but not counter-violence. And I saw almost no arrests or detentions in the whole thing. Once the fire bombs started being thrown into their ranks, I’m absolutely amazed that there still wasn’t a violent response. At that point, lethal counter-force could even seem justified in some individual cases.
To me, this almost looked too game-like – thus my impression that it’s just training, and the bad guys are acting as opposing forces. There were obvious rules by which everybody played, with expectations for responses, and everybody pretty much stuck to their roles (script?). Again though, if it was real, it’s very much NOT like riots in other parts of the world (e.g. Muslims in Europe, and particularly certain groups in the U.S.). It’s become much more like guerrilla warfare in the U.S., with no rules – just the best tactics each side can come up with to defend and inflict maximum damage on the other side.