(Sigh.) It's bad enough that you've chosen to defect; it's downright evil to try to popularize the notion of defecting. The more people do this sort of thing, the more likely it is that Amazon changes their policies, affecting those of us who are co-operating (i.e., not exploiting the policy).

Amazon can take care of itself. It doesn't need your paternalistic moralizing intervention. If Amazon believes that on net having a policy that allows returns of possibly already consumed goods will produce more profit than a more defensive strategy then it can do so. Save your shaming for people who need your defence or who are being 'expolited' in a way that isn't straightforward (albeit miserly) use of the deliberately included features of a powerful website.

Something actually ethical to recommend would be the use of calibre to convert and remove DRM and then returning the book while keeping it. That's clearly illegal and something I incidentally haven't done. I've never bothered looking in to the 'return book' kindle feature for those books I have purchased from amazon. (I just use that tool for the purpose of getting things into a format TextAloud can convert to mp3.)