Nah, they're just doing their job. People have this bizarre idea that "right to protest" means being allowed to occupy public areas until they get what they want, which isn't the case.
Obviously the police have to move people on before they get out of control, and they're of course allowed to use force to do this. People don't like it, but generally that's because the police are authority figures who have the power to tell people what to do, which a lot of people cannot cope with.