Is there really racial bias in NBA refereeing?

A paper getting a lot of publicity is claiming that white referees in the NBA are bias against black players. The paper argues that "white referees called fouls at a greater rate against black players than against white players."

Mahalanobis makes some good arguments, however, against the paper. He writes that controlling for everything else "blacks receive fewer fouls than whites. So perhaps white refs aren't biased against blacks, but rather are merely less biased against white players?"