This story broke from my home state yesterday, and was all over yahoo. I personally don't know what I would do in this situation. The man was already searched, and there were like 8 cops. They could probably have wrestled him down, and went with out someone punching him in the face. 
This has been the second incident from them in a year, and the last was when they shoot and killed a un armed white guy, who was already crawling on the ground and listening to commands. This has nothing to do with race, the main officer in the video beating was Black. This has to do with a complete inept police department. Trust me I have plenty of cop friends, and their jobs are tough, but there are a ton of bad apples with attitudes and now you just give them the authority to abuse people. I usually don't comment on this stuff, because most time you don't see the whole story, but this time you actually do. Lets say I will not be spending any time in the mesa area. I also get that these guys put up with a lot, and you can have a bad day, but if this is the way you lash out you probably should not be a cop.
