If you have $10m, and you invest that really really really well, you might be making 10 to 30% on that capital. Maybe more if you're an entrepreneur investing strategically. That's fine.
But let's say you're worth $1bn, and you compound at 10% per year.. you're making money hand over fist. Add smart use of debt to that, and that's probably too much rent seeking to be healthy.
Basically, once you pass a few 100 million, I think it gets really unfair. Below.. it doesn't really matter. No one will live in poverty because someone owns $100m -- it's meaningless in the grand scheme of things. But wealth is a snowball that doesn't grow fast enough on the low end, and too fast on the high end.
The only way to fix that would probably be a global wealth tax, but I don't see that happening anytime soon.
It's surprising that people already seem to be forgetting how incredibly horrible communism was when implemented.
If you can find an example of a government's commitment to free markets directly resulting in the starvation of tens of millions of people your argument would be much more credible.
EDIT: This is re: the comment below. We've reached HN's maximum allowable comment depth.