Good question. Perhaps people just don't have that much to add. Or perhaps they have a visceral attraction to the subject matter, but can't quite articulate why. We even see with economists that many who see inequality as a problem resort to moral arguments to justify their position. I do think there is a good economic argument for greater equality, but I'm no expert. To me, the main case for why inequality is bad was made by Robert Reich, where he pointed out that when too much wealth is concentrated at the top (especially when the reason it's concentrated is because of wage stagnation at the middle and bottom, as has been the case here for far too long), then the middle class has no purchasing power except by leveraging what is available (in the run up to 2008, that leverage was home equity loans and credit card debt). Nobody has cash on hand, because the cash is all parked in a very few accounts (relatively speaking). The system requires continued borrowing (by people who can't really afford it) to support its own weight and must, therefore, collapse eventually.