Well, maybe it's a white American thing. I was raised in a very multi-ethnic neighborhood and when Asians are playing, Asians root for Asians, Spanish root for anything spanish, Africans root for anything African, etc. And I'm sure after the game the Asians aren't conspiring how they'll deprive the blacks of their civil liberty or the blacks conspiring how to oppress the Spanish. Those people live side by side with each other going on with their daily hustle and bustle. Nothing everything race specific is racism.
But, I know large number of white people who root against anything non-white. Music, sport, movie, you name it. Because racism is more of a white practice many assume if they admit they root for the white guy/girl in a sporting event because of race then they must be racist. Not true.
Except that it is racist. When you choose to root for someone because of the color of their skin, you, by extension, have chosen to NOT root for the other player based solely on the color of THEIR skin. You have deemed this other person, of a different skin color, to be inferior and unworthy of your support. It is a form of racial discrimination and by definition, racist.