The problem is not with the part of humanity that would somehow survive a future of want and need (either because they lucked out in where they live, or because they managed to move to somewhere else that they could live, without much fuss), but with the fact that the rest of humanity is not going to lay down and die, in general, and will fight and claw their way through the aforementioned lucky/prepared sods in order to try to get a chance to survive themselves, and possibly degrade the chances of survival (certainly civilised survival) for everyone involved. Not everyone will, but desperation provokes conflict, etc...
We already see it in 'normal' situations of need. We already see that people are willing to bring out the heavy weapons in far less desperate straits, just because they think it's right to do so. And what's more right than not letting yourself, your family, your culture or country or general philosophy die out.
(Oh, and we have gone to the deepest part of the ocean. Two guys several decades ago, and Cameron[1] just this year. So we haven't seen all of it, or even very much of the bits we've seen at all. So, the minor correction aside, I know what you mean.)
[1] James, not David. <insert further political comments here>