It's kind of shallow to define the middle class by income - What really defines the middle class are values, values that government progams (which replace NGO charity work, the proper source of social support) destroy.
On another note, decrying the increasing disparity of wealth in the USA seems to me no more than useless whining because:
1) What really matters are the man-hours workers, especially the lowest-earning workers, need to put in to afford basic life necessities like housing and healthcare.
2) Complaining that wealth disparity in the USA is widening, and then demanding that wealthy Americans return some of it to less-wealthy Americans, amounts to on the global scale the global 4% or 8% demanding wealth from the global 0.1%. That just looks bad.