This critique of justice shows that power and politics play into the formulation of values. This question calls attention to the strife that permeates our society because of power differences. From the home with man and wife, at work with worker and capitalist, in politics between the enfranchised and disenfranchised, in the economics between the have and have-nots, power inequality exists at all levels. If this is our only option, then Carlos Sanchez is right. Though justice exists with power, Justice is not a power construct.
Justice exists as an objective standard and ideal.
Though we may forget those standards, those standards nevertheless exist. A just society must be a society where the Other is not originarily threatening and thus enemy. The Other must be a friend. In a society of friends, power differences may arise because of circumstance and social position. However friendship transcends these conditions, in that the friend does not see himself as master.