[ruskerdax]

Copyright is not a form of cooperation. It is a threat. If you copy something without permission, you risk retaliation that is, ultimately, backed by violent force. It is hardly honest to call something "cooperation" under these circumstances.

[type0]

Proprietary software can be downright dangerous if you tightly integrate it in your work and the vendor suddenly goes away or shuts down the software. But this has nothing to do with copyright, Software Freedom Conservancy defends GPL for the copyright holders that they represent.

The biggest issue with proprietary software is the unbalanced relationship with the vendor that it implies.

[marssaxman]

One might speak of "cooperating with the hijackers", or even more commonly one might refer to "cooperating with police officers", even though such cooperation in both cases has been compelled by threat of force. Cooperation would ideally always be a consensual collaboration but common usage of the word would not seem to require it.