when you're born, you aren't physically attracted to anyone.
to be physically attracted to someone, requires some theories about why that person is physically attractive.
we learn these as we grow up. we figure out why certain things are physically attractive.
most guys seem to be physically attracted to woman of all races (at least in movies and in California). even though they look totally different. and also, if they saw a woman of a new race (still human), they would see her as physically attractive right away. (assume she's not fat or ugly)
this means the guys are physically attracted to some qualities common to all women. so, they see these qualities in the new girl, and the racial differences don't change them, so she's hot.
obvious candidate qualities include: breasts, ass, pussy, height, hair style (women of diff races can have same hair style, to a large extent), being skinny, and anyway you get the idea.
what if someone was not quite so indoctrinated as to find anything human shaped with breasts automatically hot?
well, for one thing he would focus on personality more. but lets ignore that. lets say he grows up around only white people. probably, he will find at least some of them hot. but for his own reasons.
now, say he meets some asians. it's totally possible the reasons he found the white people hot will be something asians are physically different about.
for example, if you were making up hotness criteria on your own, you might end up finding certain face types hot. asian faces look a bit different than white ones. it may seem subtle, but it wouldn't if you were really focussed on it.
after some time, our test subject could create some theories about asians being hot too, and become attracted to asians. but these would likely be something exclusive to asians (because if whites had them, he already would have theories about them).
and then if he met some blacks, but they aren't attractive at first. etc
i wonder if this person would be accused of racism. i wonder how many people warp their views on what's physically attractive to avoid being "racist". and i wonder how much sense it makes to find something everyone has very attractive.