I've only ever pondered interracial couples from an ethnographic point of view. I've studied a lot about the different ethnicities of the world and how they came to be from a geneological perspective, over vast lengths of time. The modern era is really amazing because ethnicities are converging and diverging in ways that are historically unprecedented.
On an individual level, if two people are into one another then who cares about acceptability?
Beyond racism, I think there is also the traditional notion of in-tact lineages that has stuck around since the nobility days. Most of the world's wealthy families still forbid their children to marry outside of their race and noble class. I used to know a guy in New York whose parents were cousins, and their parents were cousins. They were from Jordan and their families still believed in pure bloodlines. He ended up getting disowned because he refused to continue the incestuous tradition.
So while we are talking about interracial marriage, what about marriage across class? Is it acceptable for a rich person of "noble" background to marry a poor person?