Read the article carefully. The student that filed the complaint wasn't the one who she mentioned in the previous article. It was someone she had "mentioned fleetingly" -- so looking at the previous article [1], it might be the grad student that the professor had previously dated, and that he subsequently filed a lawsuit against. His reasons for doing so are not mentioned in the article.
I fail to see how mentioning that the professor filed a lawsuit against someone he had previously dated is retaliatory. It is a simple statement of fact, and if anything, paints the professor in a bad light.
[1] http://chronicle.com/article/Sexual-Paranoia-Strikes/190351/ (paragraph starting "The aftermath...")