What you describe in your OP is racism pure and simple. But people of course like to make excuses.
Saying I'm usually more attracted to black/asian/white guys is fine. But to say I would never date black/asian/white guys or I don't find black/asian/white guys attractive is just racist.
Its like being more attracted to brunettes or brown eyes but I will still date someone with black hair or blue eyes. And don't even try to compare it to being gay or straight because its not the same and you'll sound stupid