Probably because having Asian heritage does not make one immune from being racist? Certainly there are various Asian supremacist movements within Asia.

Within the US, it is still just a matter of desiring a race-based hierarchy - they sure as hell don’t want equality, nor to be at the bottom along with everyone White Nationalists seek to oppress, so though they know that as a minority they won’t ever be at the top of such a hierarchy, they hope to end up in second place.