Again, I don't think it is necessary to debate the legal implications of removing DRM from products you own outright. It's complicated and it doesn't really matter -- if you as a mod don't like what was posted, you're well within your right to delete it.
That being said, you've certainly misrepresented what I posted. I did not explain anything about erasing a watermark. I suggested a tool that allows for decryption of encrypted pdf files -- what anyone does with that is their own decision. In fact, my suggestion was in direct response to people who were interested in editing the file to add in their own text or reflow the text however they see fit. Likewise, I definitely never suggested MMP makes anything "totally free". Rather, I echoed the sentiment that distributing the files without DRM would be preferable -- it is very simple to work around the DRM for those interested in pirating the content, so it only ends up serving to annoy those who have paid for the product and wish to manipulate it in some way. It's not like there aren't a rash of publications (not to mention other media) being distributed without DRM these days; it isn't a requirement for copyright protection purposes or digital distribution generally.
And if I'm not clear enough, I'm absolutely not (nor was I ever) "suggesting a form of theft."