I grew up in the southern United States - Nashville, Tennessee to be exact. I too have noticed what was written in the article White reactions to interracial unions between people of color.
I'm Black, but on my father's side my ancestry is Scotch, Native American and African. On my mother's side it's Irish and African. To most whites in Nashville an African American is someone who is a clown, dirty, unread and stupid. When someone here, who is Black, looks the least bit different from what is perceived to be the norm - no matter how fair or dark you are - the question instantly is "what are you?". I always say Black, or African American.
My coloring is like that of a penny, and my hair is jet black and medium curly when not relaxed. I have thin lips and a small, sharp nose. I'm a little on the heavy side. When I told a white girl back in high school what my ancestry was she said, "I don't think that's right." I asked her what she meant and she stated that Blacks should only marry among themselves.
When foreign people come to this country, whites instantly begin brainwashing them against us. People who've had no prior contact with African Americans are taught to hate us.
I attended a workplace diversity training about a decade ago. The couple who taught the class was a married couple. She was from India and he was from Mississippi. She told me that as soon as people like herself immigrate here they are told not to mix with American Blacks in any way, and certainly not to marry one. They are told not to live in our neighborhoods or buy from our stores - in short, as little contact as possible is to be had with us.
I believe it because within the last few years Hispanics have flooded Nashville and have filled up all the older white neighborhoods. The whites in some cases have begun to flee from them. The Hispanics haven't even begun to enter the Black neighborhoods. They've been told not to. I almost know it as a fact. Nashville now has the flavor of a Texas border town which I like, but these people don't really mix with us. I see them at church (I'm Roman Catholic). Some are hostile, most friendly, some just interested in Blacks because they are unfamiliar with us.
I don' t think white people want us to mix with other minorities because currently it might not effect the purity of the white race, but it could a generation or two down the line. The hybrid offspring of such a union might be more appealing to later whites (mixed unions between whites and the offspring), and also looking at this from a different angle it would make the Black race larger and other minorities more empathetic with us. All of this would be threatening to American whites.