I re-read the article again after seeing your follow up post, and she really is quite venomous in her jealousy rant. To be less polite, reading that link to me, came off as "white woman bitching". If you sum up her points in a shallow and crass manner, she basically said "After 9 months in Japan, I concluded that Japanese men are pussies. They are also close-minded. So my inability of not being able to date someone in Japan is totally other people's fault, not mine." It is not just shallow, but quite ignorant. Look at this line: "underemployed, socially-awkward, samurai-sword-collecting neighbor, Kevin. But in Asia, dating rules defy all logic or evolutionary law. In Asia, the nerd is king." Seriously? The she follows up with: "These men wouldn’t have been able to score a date at home if they’d been a calender but in Asia they’d nabbed the prom queen. They were true success stories. Who could blame them for taking advantage of a magical loophole that allowed them to date women out of their league?" Wow, bitter much? Anyways, I'm just discounting her "article" even further. It is quite a work of "everyone else is wrong, it's not me" whining.
These days "circular reasoning". Just natural acceptance over time because it is so prevalent in the media. So you're asking about how it came about in the first place.
Daughters in Asian societies are(were?) expected to be "married away." When they marry, they are expected to join the other family. Certainly that has changed some in modern times, but speaking from general expectations and tradition, daughters were not expected to retain your family lineage. Sons were, and thus it is far more vital that a son carries on the family name. A traditional Japanese woman understands these expectations because that's how they were raised. Marrying a Westerner whom will bring language barrier and different cultural expectations would dilute the family tradition.
I know the authur in the link you posted and you both used the term "Westerner" but I think the subject at hand is also very much racially based, not just culturally. The US census results I mentioned are all figures about race.
So how did the reciprocating prejudice start? I'm not a sociology major, but I would say that just as many social and cultural trends go (which are all learned behaviors), it's a matter of people experimenting and pushing the envelope of what used to be acceptable. Obviously the two sides (white male, asian female) felt something was lacking or they desired something that they believe they couldn't find in their immediate social environment. From the white male's perspective, I would say it's about expectation of a mate that is more devoted to you (than you are to them?). From the Asian female perspective, I would say it's expectation of romanticism.
If the expectations match up, or at least are not in conflict with each other, the coupling gets off the ground. White males and Asian females have what no other racial combination has, which is that reciprocating prejudicial expectation. Of course, everyone is an individual. No one person is just like any other. These are all generalizations and while prejudice exists in all aspects of life, one must morally check oneself when dealing with any other human being, whom is an individual, just like oneself.