There are something negative things I've noticed over the years about a certain subset (not all!) of Asian gay guys. Warning: generalizations based on anecdotal evidence incoming; usual disclaimers apply.
I've found that, a lot of times, East and Southeast Asian potato queens/gaisen/whatever they're called elsewhere -- in short, Asian guys who are primarily or exclusively interested in white men -- can be quite neurotic and emotionally immature. They instantly try to glom onto any white guy they're halfway attracted too, and can be very clingy/needy in relationships. In my experience, SE Asians (Thai, Filipino, etc.) in particular can be persistent (not to mention non-consensually grope-y) almost to the point of being pushy/aggressive if they're trying to pursue you.
In the case of guys who actually live in Asian countries (i.e., not the US/Canada/Australia/etc.), if you're not interested (and I don't mean blanket statements like "not into Asians", just when you're not into that particular individual), they're often oblivious unless you flat out tell them so. I'm not sure if it's a language issue, cultural differences, or just persistence born of horniness, but such types simply don't seem to pick up on "not interested" signals short of out-and-out rejection. And they really don't handle rejection well -- they can get extremely pissy/sulky, to the point it's almost childish. I rather suspect many of these individuals end up moving to predominantly white Western countries if they can.
In the case of Asian gay men who were born in Western countries, this is also the same sort of person who constantly cries about how racist white guys (and it's only ever white guys they cry about) on Grindr won't fuck them, yet themselves wouldn't give a non-white guy the time of day. They'll make bitter, catty comments about white guys on Twitter all day long, yet mysteriously only ever seem to date white guys when they do manage to land a partner, even when there are plenty of men of other races around as well. I'm sure it can be frustrating having to deal with rejection more frequently because of one's race, but the combination of hypocrisy, entitlement, bitterness, neuroticism, and insecurity is highly offputting.
(Incidentally, I've noticed similar traits in similarly white-guy-obssessed individuals from other non-white demographics, but that's a discussion for another thread.)
I want to stress again that I'm not trying to paint all, or even most, gay Asian men with the same sweeping generalizations -- any racial or ethnic group is going to have its bad apples. I've just noticed that Asian whitey chasers in particular generally seem to have a lot of personality traits that make them offputting as people, entirely apart from the question of physical attraction.