The “angel” here is,  as  Forbe’s reads Walter Wink’s exploration of “The Powers”:

Walter Wink’s concept of “the powers” in which he describes that there is, in a sense, an angel of every nation. “The angel or spirit of America,” Wink writes, “stands, as it were, before God; it bears the knowledge of that to which it is called. The angel of America is thus not identical with the present or past injustices of the nation. It always bears the divine judgment and calling to become what it is meant to be.”*

For Forbes,  he sees Occupy as the people calling the nation to the carpet;  to live up ,  as MLK put it  “to the true meaning  of its creed”,  and this ,  “that all men are created equal”,  cannot be achieved in the present and longstanding widening gap between poverty and wealth.  King saw immediately upon the SCLC’s  gaining historic advances in Civil Rights,  that this is also tied up with the obscene investments we were making in becoming a “purveyor of violence throughout the world”,  and also in our “glaring contrast between poverty and wealth”.  His opposition to to the war in Vietnam,  and his building a campaign to bring the plight of the poor directly to Washington DC,  seems to show a natural bent toward the inevitability of the present passions being expressed in Occupy.

The Occupy Wall Street project feels like a burning ember that might light the torch of justice and inflame our longing for freedom. For some time now, many have wondered where the power would come from to interrupt the obscene widening gap. It did not appear that the government could mobilize itself to be impacted by the angel — political protectionism seemed to preclude an awakening to the unfinished business of a democratic society. We have been forced to observe, literally and metaphorically, the collapse of a major bridge, the general decay of our infrastructure, and the consequences of natural and manmade disasters.

http://www.huffingtonpost.com/rev-dr-james-a-forbes-jr/angel-occupy-wall-street_b_1084071.html