RE: Multi Culturalism vs Multi Racialism - SOLUTION
I tend to agree that values are the strongest factor in societal cohesion and stability. I find the leftist position that genetics are irrelevant to be absurd and deliberately choosing to pretend that it is not a factor renders their arguments invalid or at least superficial.
The interaction of culture and genetics on a society over the long term is complex with each shaping and selecting for traits in the other. While it is clear that the problem must be considered in its entirety with both culture and genetics, no simple solution is obvious. Perhaps the emerging ability to author our own DNA will help bring the problem into enough focus to make progress on it. Using it as a platform to virtue signal certainly wont move anything toward a solution.
Then you haven't studied how tribes work. While it is true that there is some pre-built racism inside people, people naturally hate what is foreign, that is not permanent and it can be easily altered.
For example have you seen those instances where basically you have chickens raising ducks or one bird raising the kids of other birds. It is possible for 1 race of people to embrace another race, almost entirely, even biologically, not just intelectually.
So when you put a lot of kids together in a kindengarten who come from different ethnicities or different races, it is possible for them to bond together and treat eachother as 1 tribe or 1 group of allies.
There is nothing in biology that is preventing racial mixing. In fact it might even be encouraged biologically since the bigger and more rich the gene pool is, the better offsprings you could make.
So people have been mixing naturally for thousands of years, and the only thing that really stood in it's way were silly religious customs.
I agree, people can be conditioned to accept or reject other races. It is not at all clear to what degree race blending is desirable. You mention that it might be biologically sound to race mix because of the rich gene pool. On one particular scale, that is true and reflects the mathematical underpinnings of diversity. However, if that behavior is looked at at a longer scale, and the behavior and resultant gene pool is allowed to reach homeostasis, the richness of the gene pool collapses into an indistinct average and diversity collapses with it.
A more robust diversity preserves and isolates a portion of each distinct branch while allowing additional diversity with some mixing. Each genetically distinct branch represents thousands to hundreds of thousands of years of vested evolution. Each branch may be best thought of as a resource for the human race that is a Darwinistic hedge against a particular set of catastrophe which only they hold the key to survival for. Policies or trends that diminish the maximum diversity , particularly that infringe on the distinctiveness of the sub-pools, are provably detrimental to the robustness of the gene pool in the long term.
Wiping out real diversity in service of multiculturalism is a poor trade to make its proponents feel like they are virtuous. Even if race-mixing via multiculturalism succeeds completely in its goal and a brown world is achieved, people will still kill people. Instead of skin color, it will be for a random reason like how they style their hair different.
The real problem is that the world is filling up and homogenizing. All of the personal and national identity crisisi that are boiling to the surface now are part of a complex instinct system that nature has provided us to counter over-homogenizing our gene and meme pools. We need good boundaries so we don't have to resort to bad boundaries like wars, hatred and killing. They must protect viable pools of distinctiveness while not encroaching on other pools.
There is some merit to how this fellow formulates the problem and solution:
https://www.youtube.com/watch?time_continue=506&v=ye2tDpgU764