- Only the copyright holder can effectively enforce the license on a particular piece of software
- They are in a better position to enforce the GPL than most users
And yes, the reason for the existence of copyleft is specifically to disable the powers granted by copyright that can be used to attack the users' freedoms.
So your language here is the language of control: "enforce", "disable", and "attack" prevention.
The point is simply that there is a power discrepancy between copyright holders and everyone else, and that by limiting power the copyright holders are exerting control over what happens to their creative expression.
I don't really understand why this is contentious, I just see it as a fact about the GPL. The FSF routinely refers to BSD-style licenses as permissive, which means the GPL is restrictive in comparison. "Restrictive" is another way of saying "controlling".
The view of the FSF is that, in the case of software, that power discrepancy is morally wrong. So copyleft was established as a method to disable it.
In this context we don't consider "restrictive" as the opposite of "permissive." The ones who are trying to restrict users are the proprietary software companies. We need to use certain language to draw attention to this because proprietary software developers are trying to downplay the fact that they are restricting their users. The only reason the GPL is not "permissive" is because it does not permit them to restrict users.
- Only the copyright holder can effectively enforce the license on a particular piece of software
- They are in a better position to enforce the GPL than most users
And yes, the reason for the existence of copyleft is specifically to disable the powers granted by copyright that can be used to attack the users' freedoms.