The argument is that freedom is often restricted if the end results is harmful.
Proprietary software depend on copyright to prevent owners, which today often mean property owners of physical objects with DRM in them. Property owner is deprived of all rights that personal property is normally given to their owners. That power is instead taken by those that produced the object.
If sale of property actually follow traditional first sale principles and gave the new owner rights which used to be naturally aspect of private property, then practically all freedoms under Richard Stallman definition is given. You don't have to give away the apple (in the classical example), but once sold you can't have copyright or patents preventing the new owner from using the apple to grew a orchard.
Yes, because you becomes dependent of the good will of the seller if you encounter bugs, limitations, incompatible hardware or if the OS updates in incompatible ways.
Isn't that comparable to going to a restaurant where they don't give away their recipes? If you encounter a problem with one of their meals you are dependent on their good will to change it for you. Isnt it that you are just using a service someone provides? Or are you enslaving yourself the moment you walk in a restaurant where they keep their recipes secret?
If you use FOSS only, you still remain dependent on the maintainers of your stack since realistically speaking you don't have the time to understand and hack every piece of software you rely on.
Just because you yourself cannot be competent in everything, does not mean that being dependent on a monopoly is the same as having to buy certain things from people who are more competent at producing or maintaining them than you are.
Noone guarantees you that a year from now you will be able to find anyone who is willing to fix your plumbing. That does not mean you might as well have proprietary Microplumb products installed in your house that noone can repair or extend without permission from Microplumb Inc.
That's just the consequence of professional specialization. But the expected consequence with FOSS is that, if you can't or don't want to do it yourself, you can always pay a third-party specialist to go in and fix your copy of the software. In fact, it may be further expected that in this case, you'd have multiple competing specialists to choose from - just like it is in e.g. appliance / home / car repair, where you can go to whichever repair person you like and they'll fix stuff for you.
You can observe that most software is leased, not sold, thus restrictions apply. And indeed - the same holds in physical world; if you're the house/appliance/car, you might not be able to use it the way you like, or get whoever you like to repair it. But that's precisely the problem! Renting instead of owning has serious drawbacks, and Stallman is fighting against those, trying keep us at something more akin to personal ownership model.
There is nothing in the GPL that prohibits charging money for your software. You just have to provide the source code and allow users to make modifications & redistribute.
The existence of bittorrent means that anyone that gets their hands on your software can give it away for free, effectively making it impossible to sell it.
