As said above – you only see the end part of the video – and eveyone says "that cop should have tried to calm it down, etc etc etc…."
Look at it this way – realistically. The woman Jwalks or whatever they call it in the USA, officer approaches her to speak to her about what she's done – her reaction then determines which way the rest of the incident goes. She ends up resisting arrest, presumably on the basis that the verbal precursosrs between the cop and her were unsuccessful. As the cop attempts to arrest her, she starts to fight with him. At this stage her friend joins in, plus it looks like other people that are present may also be with the woman in the pink. The cop has a split second to react – he has to live with the consequences of his decision.
I'm not saying the cop was right or wrong, i'm not saying his reaction was over the top or justified – all i'm saying is that until you've been in that sort of situation you really cant judge.
I am a cop – although I do not agree entirley with the way things are done – I think people would be very unhappy if we went on strike for 24 hours. And as an example of how things can appear – I remember stopping a guy in a car once to tell him to put the seat belt on his child in the back seat. I was very calm and reasonable, and tried to explain that it was his responsbility to ensure the child was strapped in, and that I had no intention of giving him a ticket – it was merely advice. He then spat in my face through his open window, tried to hit me with his door and then tried to drive over my leg. My reaction to this was to drag him from his car and after a struggle he was arrested for various things. How easily could this little story be headlined "Over zealous cop beats and arrests father infront of child". if only the part from me dragging him from the car was shown. I'm sure people would say I had over reacted etc. However had the public witnessed the entire incident i'm sure their reactions would be different. We are quite lucky in the UK in that generally the public are reasonable understanding people, provided they know all the facts – its just a shame only one side ever gets aired.
The media is rubbish – and people would do well to try and see it for what it is, biased and unreliable.