"I believe the concern of the UN, and others, is that rich nations will monopolize the moon and its resources.

Without the rich nations, NOBODY will get at the moon and its resources. For that matter, without the wealth and technological skills of the West, damn few Third World nations would have any kind of industry at all in modern times, and the leaders of the Middle East would not be driving limos around.

Sure, there's going to be plenty of folks who will harp about the "heritage of all mankind" once someone else has busted their ass to actually make some money off the Moon. Someone is always willing to share someone else's wealth.

In point of fact, the wealthy nations developing the low-cost technology and capacity for extraterrestrial development is what will make it possible for others to have access to these resources. This has been true for many other fields of development and industry."

I think this a rather gentle response. I think that there are people in the UN who want to stop anyone from "getting rich". Getting rich is seen as "some grave injustice". Anyone getting rich should, at least, pay these UN people for doing such a horrible act as generating wealth. The idea that someone might find something valuable and not be "properly taxed" and restricted with laws is their worse nightmare.
They think, 'Why should some vile Capitalist "steal" money that could be made by some "good" socialism entity'.
In their world view, poor countries are poor because the richer countries steal from the poorer countries.
Anyhow, this is all rather small and petty, and is not really the problem- we could very easily ignore these idiots. The real fundemental problem is the very nature of human beings: humans fear the unknown.
Everyone fears the unknown. Some people deal with this fear by facing it, and they actually enjoy being afraid. And of course, after while they develop a shortage of "scary things"- because the known unknown become known- so they seek out other scary things. But this isn't average and calm behavior- it's generally thought to be "irrational behavior".
The route to space runs right through the core all fear, it will be seen by others as irrational behavior.
Bring it on.