Racism is not confined to white folk. There are many, many blacks that do not like whites at all and discuss it openly among themselves. When a stable, employed black man marries outside his race it can be seen as a betrayal in a culture where many men are unemployed, drug addicted, and repeatedly incarcerated and the pool of good husbands and fathers appears smaller.
There are unhealthy mixed race relationships and because of that some people stereotype those who are in a mixed race relationship. Some successful black men see a white girlfriend or wife as a kind of trophy. Many chubby white girls date black men because 'thick' girls are considered sexy by many black men, whereas younger white men often prefer the girls they date to be very thin.
Of course none of this is may have anything to do with why any given couple are together. Many times they share a faith, common goals, love and all else that any healthy, happy relationship shares.
I knew that my husbands family was bigoted. We simply did not share my ethnic background with them. My family lived 2,000 miles away. Boy were they surprised when they found out later

Funny thing is they are so trailer park trashy... it is beyond hilarious to see them attempt to elevate themselves above others by virtue of their skin tone. What a weak a pathetic thing to hold out as proof of superiority, ROFL.
My kids are all college educated and the darkest one is the Ph.D. just coincidentally. I noticed a lot of the people in our all white church were shocked at meeting my kids (they were grown when we joined)... presuming we were a white couple they couldn't figure out if we had something in the wood pile, if the kids were adopted, or if I'd been married before. Watching them try to slip in the questions was a riot. One lady admitted she thought it was Don, since he's Cajun... and most of them... well you know...