As with most book bannings, the reasons are going to vary widely across the country based on the beliefs and values of individual communities. Some will say it's because of language, others because it influences students to behave badly toward teachers.
In 2001, the board of South Carolina's largest school district voted to remove the book from its class reading lists, but it was allowed to remain on school shelves. You have to understand that people react emotionally to things they hear about books, movies, etc., and don't always make informed decisions in these matters. For example, one of the member of this board had never even read the book.
This book, which was published in 1987, was the 4th most challenged book that year and was 64th on the list of the 100 most challenged books during the 1990s.
Oddly enough, despite all of its controvery, the book has won numerous awards for its storytelling and for its careful consideration of a relevant issue prevalent in our society, school violence. The following is a partial list of award for this book:
ALA Best Book for Young Adults--l976
Massachusetts Children's Book Award--l982
Alabama Young Readers Choice Award--l982-83 86-87
Nominated for California Young Readers Award--l982
Selected for Librarians Best Book List, England--l986
New York Times "Best Book for Children"--l988
NBC Movie of the Week -- 1997
Nominated for Edgar Allan Poe Award
The pros and cons for banning any book are really personal opinions. What one person sees as a con, another may view as a pro. I don't believe you should state any opinion as a solid pro or con. Any opinion either way should be presented as such.
I hope you have read or plan to read the book before presenting your own story about the book's history as both a challenged and honored story.