I've done some further reading on this, and it seems a lot of feminist and controversial books that have gained literary recognition over decades have also been de-ranked by Amazon, among them D.H. Lawrence. Wtf?

http://www.edrants.com/amazonfail-a-call-to-boycott-amazon/

Additionally, while the books have been removed from search engines and best seller lists, all their KINDLE versions remain. Clearly Amazon is trying to still make money off of them.