Regarding police interactions with the public, I would like to defend the officers' point of view.
When an officer issues a command to raise one's hands or grab the wall it is not a request, it is an order. It's not an offer to start a debate, question the order, spit on the officer, kick the officer or assault the officer.
Anyone who decides to assault an officer should be prepared to suffer the consequences, including death. When officers come to fear for their own safety or the safety of others they most likely will take appropriate action.
Unfortunately, this happens very often in the African-American community. A sudden movement to reach a cell phone to record the interaction could be interrupted as reaching for a weapon. Similarly, yelling at the officer is a sign of disrespect and any sudden movement will result in a reaction.
So remember: An officer's command is an invitation to obey, not to debate a lawful order.
J. Michael Collins, Reisterstown