Why was the book prince of tides banned?

It's usually contested because of a graphic rape scene as well as the use of derogatory language, which includes cursing and racial slurs.

Suspended from the Nitro High School in Kanawha County, W.Va. honors English and Advanced Placement literature classes (2007) after parents complained about the book's scenes of violence, sexual assault, child rape, suicide, and more. A Kanawha County Board of Education member suggested the institution of a book rating system. Eventually, the book was approved for return to the classroom, as long as students are offered alternative texts. Source: Jan. 2008, p. 42; Mar. 2008, p. 80.