It is surprising that people don't see their condemnation of interracial relationships as racist. By definition, they are arguing in favor of segregation rather than integration. My wife is Asian, and we have been together for almost 36 years and married for over 33 years. I wouldn't change anything except wishing we had met sooner.
It is true she is no longer "culturally pure" and neither am I, but not because we have adapted to one another's original culture, but because we embrace any idea that we find beneficial without regard to which culture it comes from. Living in the US for more 60 years exposes one to many good ideas that don't originate from this country and others that do.
Every aspect of our lives shows an openness to the culture of others, even if every aspect of some cultures doesn't fit with ours.
The one thing I would point out is that in our nearly 36 years together, it has been immigrants to the US that were quicker to suggest that inter-ethnic relationships were somehow wrong (like my wife's parents, who continue to live in Asia, initially were). But perhaps that is because many immigrants come to the US for the economic opportunity and then find their children assimilating into US culture.
For those that have not seen the Disney movie, "Elemental", I think this movie does a good job of presenting this experience.