One of the instances of which The Color Purple was banned was by the author, Alice Walker, was in Israel, as recent as 2012. Walker apparently argued that Israel was, and likely still is, engaging in separatist and conflicting actions against the Palestinian people, and thus prevent the publication of the novel in the country. Walker is associated with the "Boycott, Divestment and Sanctions Movement", an organization striving to put pressure on the Israeli government and people to respect the rights and property of the Palestinians. This is an instance in which the author herself is preventing a book from being published in a certain country, effectively banning it to a certain extent, for a political and social cause.
This decision seem unlike any that this class has examined, as most instances of banning do not come from the author, but rather disgruntled citizens and critics. In this case, the author seems to want to bring about change by preventing access to material, rather than using the material as a means of change. Such a decision calls into question the overall intended impact of the novel, as if the author prevents it from even being accessed by those citizens the author believes stands in contrast to the arguments of the novel.
It could be that Walker simply seeks to prevent Israel publishers from financially benefiting from the book's success, rather than trying to prevent the Israeli people from reading the book. But one must consider the implications of preventing publication, as it must nonetheless restrict access for a large portion of the population who may not have the means to purchase it from international distributors.
It is clear that Walker's novel is meant to argue in favor of a more equal society, doing so through the depiction of characters who overturn traditional beliefs about their status in their respective societies and communities, but one must question how effective such an argument can be when it is denied to those whom the author believe reject it's ideas the most. A novel that champions a belief, any belief, and is then denied to those who dissent from it, is not really acting as an argument, but merely a celebration. In such a circumstance, apparently only those who already agree with the positions of the book would be able to read it, and thus the author is, in some cases literally, preaching to the choir. Such a work would serve to consolidate a base, a group of people who strongly support the notions of the book, but would do little to bring in new supporters from other areas.
Once again, the decision may have been financial rather than ideological, but this form of self-censorship calls into question what Walker's intent for the book is. Is she trying to argue in favor of an equal society, in the interest of convincing those who may have an opposing viewpoint to be more open to her ideas? Or is she merely writing a novel which celebrates ideas already championed by its viewers, which ultimately has little impact on society?