Actually, something akin to "I could never be attracted to x race" sounds a lot like judging that race. An entire race is a lot of people to be able to state that none of them are attractive/eligible to you merely because they belong to said race
That's quite stupid yeah, there's some completely gorgeous african women and the pattern will just increase for our standards now that we live in a modern world and they're trying to emulate their nemesis, the white anoretic woman that we so love.
And their skin is awesome, caucasian girls wish they had that.
The prejudice also happens for social reasons, meet some upper class girl and chances are race won't matter much if she's into the same things as you are and there's a connection. Sadly, perhaps due to opportunities not being the same that's not as common to see outside Africa.
In Africa it's more common because public careers have to front locals (obviously) and there's a lot of money. Upper class african girls in Africa are often seriously hot and, unlike a lot of them here, their accent is not very pronounced.
Accent is also a factor, I believe. Texan girls are also probably not popular if the accent is overdone.
That said, I also think the whole "oh I won't touch an African girl" is not the worst you can do.
Throughout the civil wars in africa ultra-racist men always slept around with indigenous women regardless of how racist they were (or were they mostly racist because that was cool and as to not lose face to their colleagues? mix of both, actually - but they certainly didn't think too much about it). The issue was that they didn't respect them (some thought of them as whores, while a lot of them weren't), didn't think of them as human beings or were simply too cowardly to admit it to the world when they returned home that they had offspring there.
The biggest racist I've ever met was an uncle of mine, whose conversations always went around the equivalent of "them niggars" but... his wife was black. I once pointed that out and he quickly shut me up with "your aunt is not black", she was. He also died of a heart attack days after she did for being heartbroken I guess.
Before her, he had another relation with a black woman and had a kid with her, although they never married he did the right thing and supported her and the kid, brought them to europe from africa after the war and all that, raised them, the kid had a father and interacted with the son of his wife as a brother, he was never adopted and was raised by his mother regardless. anyway he clearly did some things right for the realm of the time.
As a kid, I was oblivious to it, and the dude sure sounded racist, but... he didn't consider black people close to him black and... Fact is he did stuff for them that I never saw anyone "racist" do. It was just his way to express I guess. I didn't like it and I don't, but I've kinda grown to respect him after he passed. I find a lot of people are not in the lines of "I'm not racist. but..." quite the opposite. They're obviously racist, but they don't consider people they know to be of that race, no matter how delusional that sounds. Obama springs to mind, how many people really think of him as a black president? (sure, he's mixed, but so was my aunt)
The normal that happened back there is... there's a lot of mixed "children of the war", that suffer from racism from both parts, locals call them bastards and joke about where their fathers are because they know they've been abandoned by them and white people... Well, white people in Africa can be very mean, I've had friends whose housekeepers, before they arrived were beaten by the white family that was there, and that just happens. If you want to be racist you go to Africa and if you have money and do it indoors you can get away with it.
The not interbreeding thing could also come from a mentality of abundance "I can pick, so I chose my type over the other", that's quite normal; but if you couldn't pick I don't think most people would turn celibate or look for white males. Instead you perhaps could accept it for what it was and try to see further than the skin tone and features. I know I could, but I don't make that effort in my everyday life.