As a reader, I appreciate being able to return a book I know I won't read. For instance, I got caught up in the hype over Water For Elephants and one-clicked, despite my usual policy of sampling first. When I sat down to read it and realized it was written in present tense, I went right to Amazon to return it. I *LOATHE* novels written that way. It might be a great story, but it's "not for me."
I've also one-clicked Kindle books when I intended to click the Sample button. It happens. Don't assume those who return books are dishonest.