Free software does not depend on copyright. The *GPL* requires copyright to be enforceable--purely in order to subvert the negative effects of copyright law, of course--but there is much more to free software than just the GPL. The most obvious example would be software in the public domain, which obviously has no dependencies whatsoever on copyright law. A more common example would be BSD software, where the only requirements are attribution and retention of the original license notice, neither of which is essential to its classification as free software. Software under the MIT and similar licenses could likewise operate just fine in the absence of copyrights.
In any event, this isn't about enforcing or violating copyrights. This is about resisting the user's efforts to employ their documents in ways which they may well have every legal right to use them. An unobtrusive notice that restrictions were requested might be reasonable, but the purpose of software is to assist users in accomplishing their goals. Any software so perverted as to deliberately hinders its users is an abomination.