There's an argument that permissive licenses offer more freedom.
And to that, I say - yes. If you subscribe to the naïve, individualistic definition of freedom, where everything is permitted, without restrictions.
And in the ideal world, maybe that's where the story ends. But we don't live in that world. No man is an island, and if you allow anyone to do anything unrestricted, that means you permit somebody to take someone's freedom away using force. And eventually you end up with a very unfree world.
How do you combat this? Well, with solidarity, of course. There needs to be a concerted effort to protect freedom from those who tend towards smashing it to pieces. That means, some boundaries must be set up. People who respect freedom must stand together and declare that freedom and non-freedom don't mix.
You know how the corpo kind tends to say that GPL "viral" and compares Free Software movement to Borg? Well, that shows what they fear the most. Copyleft represents this solidarity.