Once again... You do not compare apples to apples. I do not need to be sexually attracted to my doctor, so I do not care if he is black or asian (not that there are many in my city ? ). But I have to be sexually attracted to my sexual partners and I am not sexually attracted to blacks and asians, so my sexual partners cannot be blacks and asians, therefore my sexual partners have to be caucasians. Pure logic.
Furthermore my sexual partners have to have many other attributes so I can be attracted to them. They have to be young, smooth, charming, witty, cultured, refined, polished, well mannered and the list goes on and on. So what I am trying to reiterate here is that race is a pixel of the whole picture of sexual attractiveness.