Wanna be soldiers become cops because its easier than making it through boot camp
Keep in mind: the standard for justifying the use of lethal force for a cop is whether the officer had reasonable belief that he/she was protecting himself or others from serious injury at that moment. The scope is narrow - it does not take into account if the cop provoked the fight in the first place.
But Ferguson's disillusionment is not an abstract dislike of authority, it can be concretely traced back to its history. When we talk of disillusionment we need to talk about years of police abuse and mistreatment of citizens: racial profiling, trivial arrests and police brutality. And they continue to justify the community's scepticism by withholding information (the officer's name), clumsy attempts to manipulate the narrative (the unrelated story of the robbery) and attempting to shut down the media.
Not all cops are bad, but it whatever institutional policies exist to hold cops accountable is non-existent; they haven't earned the community's trust.
"Real" soldiers do sometimes use weapon-mounted optics for observation and target ID. They don't always end up shooting the people they're looking at.
Your statement about cops simply reveals your ignorance about law enforcement.
I've yet to hear a vet tell me that's an acceptable crowd control tactic. Not everything the military does is crowd control, and when they engage in crowd control they don't use all of the tactics that an infantryman at the front lines might use.
To put into less hyperbolic context : when a 'target' is standing seven feet from you, you shouldn't need to aim a sniper rifle at them to identify them through its' optics.
That said, using binoculars would convey a much less threatening impression than observing through a weapon-mounted scope. On the other hand, we don't know exactly what the tactical situation was when that sniper was aiming at the crowd. Unless you do, you're not in a position to say whether he should have been aiming at people or not.
Armed forces use scopes to gather information; this is acceptable.
Police under the influence described by the Stanford Prison Experiment (http://en.wikipedia.org/wiki/Stanford_prison_experiment) Aim weapons at civilians to assert dominance that they feel they must exert.
The action is the same, the reasoning is different.