On the book The Color Purple -- when and where was this book banned or challenged, and why was it banned or challenged?
The Color Purple, by Alice Walker, is one of the books that most often faces banning, or attempts at banning.
The most common reasons for wanting to ban this book sexual content (including the rape scene on the very first page of the book and lesbian scenes) and its graphic violence. There are also concerns about the discussions of racism in the book. Please see the second link for quotes from the scenes that have been found offensive.
I do not know of any comprehensive list of places and times when this book has been challenged, but one of the links provided below refers to a few challenges.
As with most banning of books, or movies, or any content in general, there is definitely something objectionable, in this case the graphic content and its potential racism on the book.
To add to pohnpei397's answer, the link i provided is a list of classic books that were banned/challenged. The Color Purple is challenged for "sexual and social explicitness," along with "profanity and rough language"... there are a ton of reasons there, and it even says where the book was challenged. the website is a really great site to take a look at.