Who can be racist?

I googled, "only white people can be racist"--don't ask me why--and the first hit was an opinion piece from The Harvard Crimson written by Michelle I. Gao entitled Who Can Be 'Racist'? I think it's a good article. I've been disturbed about the idea that reverse-racism doesn't exist, and that it seems to be okay to disparage white people solely for being white. I get the power argument, but there's definitely something lacking. I've lacked the motivation to work through exactly how I feel about it, but this article does a decent job.