I read Harry G. Frankfurt's delightfully-titled On Bullshit a number of years ago, so this title was self-recommending. As always, I'm extremely grateful to the University Near Here for allowing me to maintain my library privileges in retirement, and thanks to the Interlibrary Loan people who wangled a dead-trees copy up here from Rivier University down in Nashua.
It's a very slim volume, 89 pages of main text. And those pages are small, the margins are wide, and the type is normal-sized. But don't be fooled: Frankfurt is a Professor (Emeritus) of Philosophy at Princeton, and (as you would expect) his argument is carefully made and tightly argued. And, good news, it's easily accessible to anyone who (like me) can appreciate philosophical discussions at a "dilettante" level.
Frankfurt's main point: equality is not a fundamental moral good. Hence, inequality is not inherently objectionable. Arguments about inequality's dreadfulness are just about always actually about something else.
Specifically, economic inequality (whether based on wealth or income) isn't inherently bad. What's bad is that people don't have "enough" economic resources to live a decent and fulfilling life. That's demonstrably bad, Frankfurt argues, and is bad without reference to what resources other people might have.
There is a utilitarian argument against economic inequality based on the diminishing marginal utility of money: If you have merely $5, an extra $1 is a huge deal; if you have a million, that extra buck is near-negligible. Hence, utility is maximized when everyone has the same.
Frankfurt shows the holes in this argument deftly. Even assuming utilitarianism is valid (I don't think it is, by the way), the further assumptions about what money-utility looks like are false or unsupportable. (And, in any case, the specter of the Redistribution Police wandering the countryside with their Utility Meters, making sure everyone doesn't vary from equality… that's a little dystopian, right?)
Once Frankfurt disposes of economic inequality, he proceeds to take a buzzsaw to inequality by other measures: inequality of "rights", of "respect", of "consideration", of "concern", of …. In no case can "equality" be shown to be the fundamental issue. There's simply no reason to assign the same (say) "rights" to two totally different people with differing life histories, values, desires, etc. Only when we are considering generic "Person A" and "Person B" can we, kind of, argue that there's no reason to favor A over B, or vice versa. But that's working from ignorance; the actual primary moral value at work is impartiality, not "equality".