Not sure if it might have a different meaning in the original language, but I asume in this scenario asian doesn't mean the general geographical range and the countries included in it but the generalized 'asian' type of person? Japanese, chinese, korean, tai (maybe), etc..
That's my best guess as to give that sense. Since that's how most people use the term anyway from what I've seen over the years.
I guess his horniness make him forget who he is
Also, on a second note: Some people just don't find certain types of people attractive. So maybe he's not into asians (in any sense) but would prefer a western, european, nordic, etc. looking person?
That could be another factor. But i doubt the story will go that deep in this specific aspect (we're talking yaoi AND Omegaverse here, so chances for detailwork are abyssmal as is).
seme: I don't like asians
me: *scratches head* ain't you asian too my dude ??