One event is not proof that they many dozens of protests haven't been peaceful and clearly the police have assumed (probably because of intel/it being at night) that could end up violent thus have resourced themselves for it.The police will pay him off with a quite large sum because they have royally ****ed up.
This is what happens at your "generally peaceful" Palestine rallies when they reach Trafalgar Square.....
How often do football ultras instigate violence? Forgive me for thinking the police might know their audience.