I'm not against interracial coupling. However, I do view it as a way of eroding identity in the long run, especially when it occurs in multiple steps. In fact, the Australians employed this engineering to phase out the Aborigines in the early turn of the century when eugenics was widely practiced.
It is harder to claim identity or relate when your own DNA has been heavily mixed. Biracial children have always claimed that they didn't fully identify or couldn't fully identify with either side. When that happens they lose a lot more than just identity, they lose culture.
Let me demonstrate using religion. Many religions are tied to the particular ethnic group that practices it. For example, Judaism is the result of the Israelites experiencing revelations from God. Since then, many non-Jews have converted to follow the God that revealed Himself to the Jews. Many of them follow because they believe the Jews experienced this revelation even though some have yet to experience it for themselves. Because they believe in the Jews' experience, many of them later come to have their own experiences. Until they have their own experience, they follow all the religious rites and customs without the same meaningful purpose as the Jews.
For example, why do so many Hmong participate in decorating a Christmas Tree? That was never part of our traditions or customs. We do it because it is mainstream America. But before it became mainstream it was really just the Germans. But even before the Germans it was the Scandinavian Vikings who found significance in the evergreen tree during winter solstice. They decorated it in order to entice the spirits return in spring. The Germans used this symbol as an effort to Christianize the pagans.
So why do Hmong put up a Christmas Tree? If it doesn't make sense for Hmong Christians to put up a Christmas tree then it's even more baffling that Hmong atheists or shamanists do it.
The point is that when things get watered down, people find new reasons but most of those reasons are hedonistic. In other words, we put up the Christmas tree because it is fun and festive.
The same thing happens to those who are the children of interracial couplings. For example, should someone who only has 1/10 of black in them feel all that outraged that some time long ago they had an ancestor who was a slave? This person probably does not feel as outraged as the black person who is and can fully identify as black. If they do feel outraged it is because society tells them they should be.
This is why even though all human beings have less than 1% of sub-sahara African in them, many of us do not identify with blacks.
Culture is important. It is part of identity but only holds true when interracial couplings occur infrequently.
If culture is important to identity but is also evolving, then which parts of the culture are the key identifiers of an ethnic group?
Language should be #1. Language is pretty unique to a group. It is the most important but also the easiest to lose especially as the world becomes global and very few ethnic groups live in isolation.
Just think about it. Why did God disperse the people at the Tower of Babel? Why was God so against them all speaking the same language?
If you don't believe in God, perhaps ask where languages come from and why they can be so vastly different.