I think filtering in general is a totally different subject than the perception that a particular minority was specifically targetted by Amazon's scripts....but that dead horse is well and truly flogged.
I'm pretty sure Amazon DOES do quite a bit of filtering, and you probably appreciate the results. One example I can think of (and I have no information to substantiate that this is happening) would be romances. They're a high-volume, low profit item for a bookstore. Do you really want to browse the top 100 sellers and sift through 20 or 30 Harlequins? You might want to, but Amazon doesn't really want you to....if you're looking for romances you're going to find them. They don't need to put them on the front page to attract sales. There's a reason that most best seller lists only include hardbacks - they're filtering the results that they present to you and that's been going on for years, way before Amazon came on the scene.
I'd be interested in seeing what a completely unfiltered search at Amazon would be like - I'd bet we'd all be surprised at the results.