I would advice you and others to be more blunt when advancing your case.
No one – not even you – remembers if we were good or bad, why we fought and why we died...No! All that matters is that two stood against many, that is what’s important.
There are objective measures for fitness and quality of individuals, too. But it would be insulting and also kind of weak and evasive to refer to your superior figures of merit in your personal business and contentions. If it is about your personal survival or physical safety, appealing to your goodness, your usefulness, is pretty much the definition of slavishness. (I have never read Nietzsche, just seen some Western movies.)
I’m sure you can see how my point applies to cultures and ethnicities. I understand very well how one gets to the arguments in your comment when dealing with the usual pro-immigration arguments from economists.
Myself, I think it’s nice to have a nation of one’s own and a homeland for that nation, a country and state owned by that people. Why should we get to have it? Just because.
OP: To me it looks like Hanson is saying the lack of cultural variation and lack of selection pressure on cultures will – to continue with the biological metaphor – lead to accumulation of mutations and loss of function. Whatever your culture values, it will be worse at getting it. Maybe he accidentally introduces his own values to the objective disinterested frame, but it’s hard to believe Hanson would make any such mistakes big enough to cause twisting physical reactions of empathetic shame.
Hanson’s argument above sounds somewhat plausible to me. What I don’t understand is his theory that population bust will lead to stagnation in innovation. Maybe he makes the standard economist assumption of technological progress being a linear function of population (with given level of wealth and tech), which is obviously untrue. Maybe he gives too much weight to innovation in highly specialized fields in comparison to innovations that have more general and generalist applications.
That is relevant in pre-implantation diagnosis for parents and gene therapy at the population level. But for Qwisatz Haderach breeding purposes those costs are immaterial. There the main bottleneck is the iteration of selection, or making synthetic genomes. Going for the most typical genome with the least amount of originality is not a technical challenge in itself, right? We would not be interested in the effect of the ugliness, only in getting it out.