I think that's a messed up attitude personally, but at least it is a consistent attitude towards intellectual property. I could respect somebody for being consistent in their attitude - especially if they themselves are also having their work pirated. Anybody who is pirating music and movies, but they themselves do not tolerate disobeying the license terms of their own work I feel is a hypocrite.
If people ignore content restrictions by pirating works, is that not consistent with the people who uses copyright to prevent content restrictions? Is it not also consistent with people who breaks content restrictions by breaking DRM?
In each 3 cases, content restriction is problem being dealt with. Preventing, ignoring or breaking, either way its dealt with.
GPL says: Do what ever you want with the program so long no one become restricted by your actions.
If you patch it and send a proprietary version to someone, it will still be the same program. The difference will be the added restriction. The software license only uses copyright to enforce a "share, and share alike" concept.
Using copyright to restrict distribution, ala the proprietary model, is not the same as enforcing a share alike concept. They might use the same law, but the underlying concept is completely separate. Free and open source licenses are also not commonly enforced against individuals, but proprietary software is.
Or to summarize: Restrict restrictions is good. Breaking restrictions is good. Ignoring restrictions is good. Each 3 is consistent with each other.