According to the socialist academic Walter Benn Michaels, the reason that rich western liberals talk so much about racism and sexism is so they don’t have to talk so much about economic inequality. He published The Trouble with Diversity exactly a decade ago, but it feels like a tract for our times, perfectly suited as a provocation to thought as we approach the summing up of liberalism’s great annus horribilis.

Rich western liberals, Michaels argues, don’t want to challenge the economic structures that produce inequality because that might seriously impact on their own standing and wealth. Instead they insist on the elite being as diverse as the poor, as a way to justify the very existence of the elite. So, as long as the top class at Harvard shows a proportionate distribution of social diversity, one can happily ignore the fact that all the students come from money. Moreover, it’s not just that this focus on diversity distracts from the deeper issue of economic inequality. It’s worse, because the very diversity of the elite is asserted as justification for the non-discriminatory nature of capitalism. Diversity has become the moral alibi of neoliberal economics.

It’s not that Michaels is against diversity per se. He absolutely isn’t. But he thinks it misses the bigger picture when the struggle to achieve wage equality between men and women at some warehouse job is touted as a major victory when neither the men nor the women can actually live off what the warehouse is paying them. Likewise, when a battle is won for women at some merchant bank to earn the same squillions as the men, yes, it’s a victory. But both victories leave the most fundamental injustice perfectly intact: inequality.

Since the civil rights movement in the 1960s, the US has become a much fairer society in terms of race and gender. No doubt there is a way to go, in some places a very long way to go, but the progress has been considerable nonetheless. But during this exact same period, the US has also, steadily and continuously, become more and more unequal, the gap between rich and poor widening to a level that now threatens the very stability of these disunited states. And it’s in this gap that Donald Trump has turned his knife.

The issue, of course, is capitalism. And that the mainstream of both political parties refused to pull at the thread of its failures. Clinton Democrats and Bush Republicans subscribed to the view that global neoliberalism was a good thing, with Democrats combining this commitment with a (roughly speaking) civil rights/affirmative action tradition and Republicans with a (roughly speaking) socially conservative/evangelical Christian tradition.

Interestingly, of the two, it is the Democratic pairing that makes the more natural fit – for neoliberal capitalism may produce winner-take-all winners and lose-it-all losers, but it is nevertheless an economic system that is indifferent to colour, gender or creed. Which is why capitalism is sometimes held up as a means of affirmative action – eg the pink pound. If a Muslim woman is better at doing the job than a white man, the logic of capitalism is entirely non-discriminatory. She rightly gets the job. Thus capitalism is applauded as an agent of social progress. And yet the poor get poorer and the rich get richer.

It took two political outsiders to say this: Bernie Sanders and Trump. The former said it responsibly, respectful of the many moral gains that the era of liberalism brought about. The latter saw a gap and viciously exploited it, turning the resentful white poor against other poor minorities who are themselves as much a victim of the machinery of capitalism. A decade ago, the critics of Walter Benn Michaels thought he was doing something similar, playing women and people of colour off against poor white middle America. Why can’t social justice mean a commitment to both social diversity and economic equality? Yes, it can and it should. But only when wealthy liberals appreciate that, in and of itself, the struggle for diversity does little to benefit the poor.