they decry as emblematic of this supposed class envy. I suppose that could be true, but it would be hard to prove.
Instead, I think a more serious response would acknowledge the usual claims about inequality. First, a large gap in incomes is usually indicative of other inequalities, such that income mobility - or freedom, in a real sense* - is limited. There could be any number of reasons for this, i.e. in typical post-colonial 3rd world countries ownership of land, wealth and access to power is distributed highly unevenly. Even in 1st world countries, there is a high correlation between access to social capital and wealth.
A second claim, and it largely follows from the first, is that tax structures should take into account this social capital dynamic, and assume that greater incomes were born from greater access to capital. Thus, tax burdens should be progressive.
Third, and this is somewhat separate from the concept of social capital, but it is simply true that those with greater incomes can afford to pay more in taxes without as considerable a cost to their standard of living. Because basic things like rent, food, utilities and transportation make up the largest portion of lower-income families' spending, taxes will eat into that much faster than they would upper-income spending - the bulk of which, at progressive rates - is concentrated more in luxury amenities and investment capital.
Because there are many things that a government does that will not be done in the private sector, it must generate revenue somehow. Income inequality, and philosophical beliefs regarding it would need to factor in.
So those are just a few of the issues involved in the critique of income inequality, and policy response. I have no doubt that envy does play some role in this - who does not want to live like a king? Yet there is a difference between jealousy when things are perceived to be fair, and jealousy when things are not. I suppose in an ironic twist, conservatism's philosophical apology for inequality might indeed provide a soothing rational and justification for those who might otherwise feel they are on the losing side of an unequal class structure. Conservatism in this way would serve as a sort of - to echo Marx - "opiate" for the pain of extant power imbalances.
(* The issue of freedom and liberty may be concepts that the left should be more vocal on, from a messaging standpoint. The right uses them to great advantage, leveraging their historical and patriotic import, and in no small way slanders the left as anti-freedom and anti-liberty. Yet the left could just as easily stand behind those terms in criticizing the right for the same thing, albeit for different philosophical reasons.)