Why is finding certain ethnicity attractive worse doing so for any other feature? If you ask someone what their ideal man/woman is they often have a very precise set of features down to hair and eye colour (often HUGE BOOBS/COCK and weight limits are also on the list.) Some people would also list the ethnicity in that same list, is it any worse than having a fetish for redheads?
I mean, if you only care about superficial features you might not get a lasting relationship as it is more important that your personalities match, but I don't think that having a fetish over certain kinds of people is bad in itself.