The "middle class" is a post industrial revolution concept; there was no feudal middle class; the concept is a creation of capitalist production. If there is no capitalism, there will be no middle class, but more subtly, if there is no production in an economic society, there will be no middle class.
The 'inequality' complained of here is a result of declining domestic production which was brought on over the past 30 years by a fiscal context that discouraged domestic investment over domestic consumption. This middle class destructive fiscal context reached its apex under President Obama. With all the socialist and income inequality rhetoric the last eight years only saw an acceleration of production running away from America and a worsening income inequality metric.
What we need to do to help America (capitalism doesn't need help, it will move if you are not nice to it) is encourage domestic investment by reducing tax and regulation on investment; this is more important than reducing taxes generally, or reducing individual taxes, or reducing taxes on the 'middle class.' All those other tax reductions are merely feel good Keynesian sops that will not help; that will not produce wage growth for domestic workers.
Because we can't ignore the needs of an 'underclass' of unemployables that we have created though dysfunctional progressive policies, and we must provide for domestic security in a still hostile world, and because we have squandered so much in government borrowing that was never invested in anything that could pay back the debt, we do need gov't revenues.
That is why it is important that tax reduction be focused in ways that encourage production; this may seem unfair and unequal, but it is the only thing that will provide a basis to work out of this mess.