What ACTUALLY happens is that they cut out all context of what led up to the situation, and cut in to a point where anybody with half a brain could see that the cops had been giving lawful orders for rioters to disperse, for what was probably a long time, they're on a loudspeaker giving them lawful orders to disperse, warning them that if they don't disperse force will be used against them, they decide to ignore lawful orders, and force is used against them to make them disperse.
The way the headline makes it sound, they were just nice peaceful protesters, not causing any problems, and police just rolled in and started beating them.
Protest is legal, and ignoring a "lawful police order" is also legal. The police can't just tell people what to do. Neither of those things warrant being assaulted by a police officer. Your own description of what happened is that the police used force to disperse peaceful protestors, which is obviously unacceptable.