Clean Reader - Legal or Ethical?

I've been hearing and reading a lot recently about an app called Clean Reader that has been developed to, according to its developers, 'remove unnecessary profanity and blasphemy from a book.'
I have to say that this idea fills me with dread. If it's legal (and I have my doubts) then this is the thin end of the wedge for overly aggressive censorship.
The idea that someone can take a piece of work I've written and randomly change words makes a mockery of the creative process. Like all authors, I weigh my word choices carefully in order to evoke a specific feeling or setting. Change one word and the whole sentence/paragraph loses its impact and clarity.
I very rarely use profanity in my daily life, I've never felt a need for it. (Plus, as a father to two small children, I have to be careful what I say, but that's a whole other story...)
My books, however, do contain profanity. They also contain sex and violence and blasphemy. I write horror stories, for Christ's sake (oops, wonder if clean reader works on blogs?) and, to write a believable character, they need to behave in a way that is consistent with real life. So, for example, if someone is in severe pain, I believe they would resort to good old Anglo-Saxon (i.e. swearing) rather than saying something along the lines of, 'Oh dang, my leg's hanging off, that stings a bit.'
My current WIP deals with the relationship between a group of four students on a hiking holiday. There is a typical student drinking session involved, and yes, the language does get rather choice. Ever been on a student drinking binge? Enough said.
I also want to touch on the legality of this app. The makers say they have taken legal advice and that, because it performs the word substitution on the fly, without changing the original downloaded text, it is legal. I disagree. My considered opinion (and I do have a legal qualification) is that what the app does is just as much an infringement on the intellectual property as changing the source file. It's the same as going to an art gallery and placing masking tape over the naughty bits on a painting. The original is still there, you just can't see it. And I wonder how well you'd fare in court if you tried this and claimed that you weren't altering the originals, just providing a different version that didn't offend your religious and cultural sensitivities. Not very well, I suspect.
Another thought that occurs to me is this: what is the position re reviews? I mean, having seen some of the app's attempts at cleaning up the original text (a quick search of the internet provides several examples), it's clearly not very good. But if a reader tries a book and writes a scathing review based on the clean reader version, how valid is this? I mean, they haven't read the original book, so how can they review it? It's like watching Under The Dome on TV and then trying to write a review of the book. (And again, a quick search should unearth that particular shit storm. (Oops, dang it all to heck, another target for clean reader!))
I've no idea (yet) if it's possible to find out if a book has been modified by clean reader, although I'm looking into it and following the debate with great interest. If it is possible, then I shall be keeping an eye on it and requesting any of my books be excluded from it. If you don't want the language, don't buy the books. I don't believe this app is legal or ethical - how much uproar would there be if I produced an app that modified parts of the Bible? Or any other religious text, for that matter? We only have to look at the recent Charlie Hebdo attack  to see where this kind of tinkering can lead us., So, through gritted teeth: Leave. The. Books. Alone.