Copyrights are granted for and exist for a limited period of time. Once that period of time is over, the copyright ceases to exist and the software may then be reproduced, used and modified as much as any person may desire. This brings up the question of whether copyrights and patents are being abused and improperly granted on things that should be in the public domain to begin with.
There are many reasons why copyright remover software could be unethical (of course), and this is an easy argument. However, many legit users could use it. DRM is often installed that ruins or makes games or software inaccessible, and while cracks appear online for the pirates within hours, the legit users are harmed.
Generally I would say that free copyright remover software is not ethical to use and this would apply to most people. However, as a film student I could see instances were this type of software could help a student learn. Obviously they wouldn't use it to make copies, but you could use clips in editing exercises.
It is easy to lose sight of what a copyright is in software, in short, it is the cost of innovation in programming and signals to other programmers that they should focus their efforts in one area of programming or another. To not pay for the cost of the effort to innovate is to essentially send a message that future innovation will not be respected.
Removing software intended to protect the copyright of certain works is highly illegal and unethical. What if someone did walked into Wal-Mart and didn't pay for their groceries? That's the same thing as removing copyright protections on software, music and videos. This is a consumer-based society and nothing is ever free, so get used to it.