Well you must've spent your life being rejected by the Japanese? It is not like the majority of Korean or Chinese wouldn't smirk at having their sons/daughters with black spouse or Japanese spouse (shocking I know right? but it is the reality, do you know?)? or dare I say, even Arabs, or whites, or south east Asians. There will be people who look down on other people, regardless of race and nationality.

For the record, maybe you haven't met a nice non racist Japanese person yet, that's why your reaction is like that. There are quite a number of mixed ancestry in Japanese society, most of them do fine.