Amazon weighs in.

Amazon claims the de-ranking is a glitch, not policy.

I'm skeptical, but if this means they're going to undo their "glitch," then I'm all in favor.

ETA: This is a very interesting commentary.

I should add, I suppose, that while the de-ranking (and the basic principle of censorship behind it) infuriates me, it has not affected my opinion of Amazon. I didn't like them when I got up this morning, and I don't like them now.