First off Megzm is right on top of it as far as the meaning. It is obviously about racism and it was a very moving song. Its easy to forget that some people have to deal with racism daily.
Second Stupidpeople is obviously born retarded; it doesn't make you racist to joke about the meaning of a song.
Along with that note, yes, racism still exists, but the day people can joke about it without others getting offended is the day racism no longer matters because no one will care when no one is treated unfairly due to their skin pigmentation. Also, everyone knows "races" among people is a term that is false.
And keep in mind that people are prejudice against foreigners, poor people, americans, muslims, what ever reason you can pick is a reason used. The only difference is racism is more specific to the us since most all other countries no longer have deep-seeded roots in the topic. And btw I see asians and african americans be racist to members of their fellow pigmentation.