I'm amazed to note that black women face negative scores from men of all races, including their own! That sounds really disturbing, at least to a non-American.
That's because Asians are perceived as feminine, while blacks are seen as masculine. Feminine men and masculine women aren't as attractive as masculine men and feminine women.
There is in much of Black American culture a significant taboo against Black women marrying (or dating) "out", which I think is significantly influenced by a very long history of black women being viewed as acceptable for casual use, but not marriage, by white men, and the resulting accumulated history of experiences with "dating out". (There are other cultural factors that feed into this, as well.)
Indeed: active resistance to these cultural norms have range from Black is Beautiful to Baby Got Back. Anyone who is curious about these dynamics can find a rich history of stereotype and resistance to explore.
Source:
http://www.pewsocialtrends.org/files/2012/02/sdt-2012-rise-o...
http://imgur.com/V9w2k5m