The danger is where inequality in rates of improvement in material outcomes leads to inequality in moral outcomes. To borrow some rather loaded language, the more the 1% can buy themselves legal advantage, the more unjust the world becomes. If the rate of legal advantage is affected by the absolute difference between the 1% and the 99% (which I'd argue is demonstrably true - beyond a certain point you've got regulatory capture, but even before then, paid legal representation is the lever that matters here), then it's trivially true that a more materially unequal world is more morally imbalanced in the absence of a somewhat socialist government.
Yes, the poorest and the average now are doing better than they were. That doesn't make defensible the disparity in gains between the richest and the rest.
I think the historical record is against this. Specifically: before the liberal revolution--the liberal idea that all humans are equal, which was truly revolutionary--it would have been unimaginable for a member of the peasantry to even claim equality with some lord, let alone build a legal case and have it heard. Again, it's far from perfect today, but better on many fronts. I imagine that differences will continue (they're unavoidable) but the mechanisms to cope with injustice will get better.
By what mechanism? I'd say that the historical record is specifically in support of this. Civilisations start out relatively equal, inequality increases over time as wealth concentrates in elites, then they collapse either to revolution or war, reset, and start again. What evidence do we have to support the idea that we should draw a line up and to the right?
Maybe more correctly: the vast majority of humanity was equal in its wretchedness, poverty, ill-health, and violence; the vast majority of people led miserable, hungry, precarious, uninteresting lives.
Again, I'm not saying we've done all we can do. I'm not saying that many of the rich don't behave reprehensibly. I'm not saying we can't do better. But the question is: How? How can we do better most effectively? I don't think the answer is 'tax global wealth and redistribute' a la Piketty--because that's not what enriched us so over the past 200 years.
So yes, it has gone up and to the right, especially in most recent history--though, because of human folly, there is no guarantee that it will continue to do so.
This is a misconception and not what the alluded revolutionary idea is quoted by in the declaration of human rights. All humans are created equal, and I'm sure that modifier was put in not by accident, even though I couldn't explain the difference.
Point in case, one conclusion seems to be that humans are precisely not equal to each other, everybody's worth is equally indeterminate. Edit: I am biased to say this because human worth is specifically mentioned in this context in the German Grundgesetz (foundation of the law) where it's called Wuerde (dignity) and encompasses more than the capitalist idea of material value.
Yes, the poorest and the average now are doing better than they were. That doesn't make defensible the disparity in gains between the richest and the rest.