One is essentially required to defend one's copyrights and patents - that's why Disney are such dicks about it, for instance, and sue preschools which paint their characters on the wall or something. Not because they want to be, but because if they let someone violate copyrights, for whatever reason, then someone else who does it and should be taken to task over it has only to point to the case where the law was not enforced, and that's it. The company has to demonstrate a consistent and complete interest in defending their IP, even if that leads them to bring apparently hopeless, pointless, or malicious cases.