"I always stare at interracial couples in public and wonder how they met because their cultures seem so different."
The controversy over the new Cheerios ad is not about a fear of cross-racial contact in general, but the fear of a certain type of cross-racial contact -- that between black men and white women. To understand the specific nature of this particular racist outburst, we need to go back to slavery.
Do not use stereotypes to appear knowledgeable about your beloved's race. Obviously, a difference in race does exist and there is nothing wrong with acknowledging these differences, but you don't need to live in the land of labels.