How many wrongs make a right?

It's been an interesting weekend in Ferguson MO starting with Friday's revelation of a convenience-store security tape apparently showing a young man roughing up a shopkeeper while trying to steal cigars a short time before a cop shot the young man to death. Reactions to the tape were fascinating. Some cynics were happy to see the story told by the victim's family of an innocent "gentle giant" belied by the footage. It confirmed an impression that a black man who gets shot by a cop must have done something wrong, or at least something stupid. Unfortunately, many observers made an unjustified leap in logic to argue as if the young man deserved death for his actions in the store, even as the police made clear that the cop who killed the youth didn't know he was a robbery suspect. Meanwhile, sympathizers with the victim treated the footage as an ad hominem argument against the dead man, a distraction from the crucial question of the police procedure when the youth was stopped while jaywalking. In fact, no one has a right to infer from the security footage how the doomed youth behaved when the cop stopped him. If the footage has encouraged a belief, in advance of definitive testimony about the shooting, that the incident was a justifiable homicide, on the assumption that the victim was violent and menacing, than releasing the footage was an irresponsible act. Yet it will still be welcomed as a contribution to the whole truth of the story, regardless of its legal implications. Its social consequences were less welcome; it seemed to provoke new rounds of rioting and looting, including some spiteful targeting of the store with the cigars. No one approves of this yet no one can stop it. "No justice, no peace" has a compelling logic that defies efforts by community leaders and activists to turn the rhetoric on and off. For the mob, "justice" is the arrest and at least the prosecution of the cop for murder. He is presumed guilty by many, some of whom probably see any killing of a black by a white as murder, if not an act of war. Objectively, however, the issue is not whatever attitude he might have had toward a large black man but the leeway for lethal force given police everywhere. Even in the worst-case scenario imagined by police apologists, in which the victim was trying to take the cop's gun, it isn't unreasonable to expect cops to be capable of defending themselves and protecting their gear without using lethal force, particularly when the assailant, as everyone agrees, had no weapons of his own. The rules police make for themselves may exculpate the cop depending on what actually happened, but that won't necessarily make his walking away without penalty just. It's the people's prerogative to question justice as defined by police, but if they can't find a better way to articulate their questioning than to sack unoffending stores they surrender much of the sympathy to which they might otherwise be entitled. Worse, it shifts the subject back to "what should be done with black criminals?" from "what should be done with cops who use excessive force?" where it belongs. On the other hand, if mass anger is at all justified, excess anger shouldn't entirely dismiss the grievance from the minds of presumably objective observers. If the cop did wrong, you can't let him walk just to spite the looters or Al Sharpton or whoever's protest offends you. We still need to know exactly what happened, and it would help if we could agree on what should have happened before anyone passes judgment on anyone else.