Compelling presentation of evidence that more equal societies have better health and social outcomes, such as trust, life expectancy, violence and child well-being. These benefits affect all income levels, not only the poorest, and are unrelated to GDP. The authors point out that increasing wealth has not benefited people beyond the level where basic needs are met, but that increasing equality brings significant benefits. They also link their case to the sustainability imperative.
I can't rate this highly enough! Arguing for egalitarian economics is an uphill struggle against people who support deregulated neo-liberal capitalism, because it has its own myths about all boats rising, aspiration, scroungers and so on. Here's the data to grab in those debates where your interlocutor says 'it's nice to be idealistic but...'