As an Asian girl growing up in the United States, I believe I was taught by the society to be attracted to just about everyone besides other Asian men. This marginalization of Asian men has occurred, in my view, for several reasons.
First, the media never portrays Asian men in a dominant role. They are always portrayed as nerdy, geeky, brainiacs, with no sense of themselves and no ability to attract women.
In other words, the media portrays Asian men as incapable and undesirable. Second, American society has many negative stereotypes towards Asian men.
It has become a complete joke to think that an Asian man could ever "satisfy" a woman. Their "manlihood" is the constant subject of jokes and insults. For this reason, most women view Asian men as asexual and feminine.
For these reasons, Asian girl, and women in general in American society are taught to view Asian men as undesirable and feeble.
As you will see, this is the reason why Asian girls are now up for grabs... Asian girls in our society, because of their conditioning, on the whole do not prefer to date Asian men.
In one of the discussion classes I taught last year at Bangkok University, half of the Asian girls in the room, stated that they do not prefer to date Asian men. Also, roughly every other girl in the class also agreed that they prefer not to date Asian men.