I had, and I have provided a counterexample: there is no license incompatibility if you avoid GPL. That wouldn’t be true if the “virality” was a property of the copyright itself, would it?
You're wrong and you don't seem to be listening but I'll try one last time. I think you're simply refusing to engage thinking circuits because you've already installed the following in your brainrc: alias GPL=bad.
Licence incompatibility is not in the slightest bit unique to the GPL. It's simply how licences work. Other licences can seem interchangeable because they are very simple and one may stipulate a superset of the requirements of the other, so you can always "upgrade". But you can't "downgrade". You can't mix a BSD-licensed work with a WTFPL work and license the whole thing under WTFPL because you will violate the BSD licence.
Licences are only a thing because of copyright. Every single licence out there only works because of copyright. Different licences have different aims. The aim of GPL is to "disable" copyright. The GPL is antiviral.
