The 2 situations are different, in the following:
In the actual situation, the person was reported by several witnesses to be in the process of complying when he was assaulted by the police.
In your hypothetical situation, the police would be seeking to establish if the person did belong there. If the person could not present ID in this case, there are simple ways to verify ID. If the person says his name is "john smith", and the address is 25 mockingbird lane, the police can run his non-existant ID based on other factors, which would in most cases be tied in to the ID he cannot present, to check. They can query their database which should contain a physical description of Mr Smith, and other identifying information. My drivers license has my hair, and eye color, birthdate, and other bits that a casual criminal would not have. One would expect that anyone they give a gun and badge to, would understand how to ask for a name and call in an ID check.
Bob,
In many situations the witnesses were friends or plants of thsoe who came to fight me or challenge me or try to hurt me. So while this looks bad up front, I would still want to see an investigation, and see the relationship between the witnesses and the person who caused this event.
And yes, If you can question the policies, cannot I question if the witnesses are not biased?