While there is a wealth of videos out there showing very serious misconduct and unwarranted violence by these shielded government agents, this video does not seem to warrant the outrage being shown by the public. While it certainly does run contrary to our moral senses that a grown man, an armed man and a stranger should hit a child in the face, we should try to understand that the police do have a job to do that is often a difficult one. A job where sometimes what is necessary is not always what we would like to see, or admit that we might have to do the same if we were in their shoes.
In this instance, the officer claims the boy bit him. The video was filmed with a lagging digital camera in a cellphone, so it is difficult to catch the few moments in question, whether he did bite the officer, or to get a sense of how hard the officer actually hit him. Or even if he really did hit him for that matter, though it does appear so. What the video does show however is that the officer was being calm and professional, not in any rage of any sort, and even waved at the camera before the apparent bite and strike. This would seem to run in accordance with his claim. If the boy did bite him, then the officer was justified to respond.
The only other issue at hand might be whether the officer was justified in taking the boy in the first place. This is, of course, another very serious concern when we as a society have seen so many terrible examples of a child being taken away for very little cause and winding up abused, or even murdered while in state custody or in a foster home. So while the officer may have been justified to strike the child after being bitten, it would be far less justified if the officer was there acting on what amounts to a kidnapping order by a local CPS office. This does not appear to be the case either though.
Reports indicate that the boy was illiterate, did not attend school, and was living in a bus. Furthermore, he had been living with a woman for years despite a court order awarding custody to his father. So this was not so much the state taking custody, as enforcing the rights of the father, which is all too rare it seems these days.
All in all, it appears that this is actually an example of how public outcry against the police is not always justified. (Even as public outcry seems to be severely lacking in other instances where it should appear.)
Finally now, here is the video to judge for yourself: