I would be interested in reading the source of this that the author used.
FWIW, here is a report from the state of Arkansas: Only three of 699 rape cases in 1998-1999 were white-on-black.
http://www.acic.org/acic_pdfs/01/Section3_01.pdf (page 10)
I've seen many references to DOJ and FBI statistics but I couldn't quickly locate any similar tables.
I'm pretty sure this white-on-black rape vs black-on-white rape statistic comes from the 1999 Department of Justice Uniform Crime Report which was still recently accessible on the fbi.gov website. (Not sure it is still there).
CURIOUSLY, (on a different topic here) although Latinos are classified as "latinos" in the Hate Crime "victim" statistics, there is NO classification for "latino" in the Hate Crime perpetrator category. When it comes to perpetrators, "latinos" are lumped in with "whites." There is no such thing, according to the UCR (uniform crime report) of ONE SINGLE hate crime perpetrated by a latino. I saw this GLARING anomaly myself on the fbi.gov website less than a year ago! It is unbelievable. Wonder what the motive is behind this convenient "oversight." Hmmmmmmm.