The material may not be a property (an intellectual concept can not be property), but the copyright itself is a property. You can own it. You can buy it. You can sell it. I very much dislike the term "intellectual property" because it conflates a lot of very different issues. Rights like rights of monopoly, mineral rights, rights of way, etc, etc, etc, though, are legal properties even though they do not represent physical things. It is ineffective (and I would also say incorrect) to argue otherwise. You're not going to get much traction trying to backtrack 800 years of legal framework. The concept of legal ownership of certain rights is an important part of how freedom is structured in modern society and I don't think you intend to try to dismantle that.
Exclusive right to copy something (or make derived works) is not an intrinsic right. It's a right given to you by society. As above, it's great that once it is given to you, that you own it. It would suck if society could just arbitrarily take it away from you. What I think you are trying to argue is related more to the fact that copyright is not an intrinsic right. As a society, we do not have to grant a copyright at all if it is not beneficial to us. We need to do a better job of balancing the interests of all parties.
Exclusive right to copy something (or make derived works) is not an intrinsic right. It's a right given to you by society. As above, it's great that once it is given to you, that you own it. It would suck if society could just arbitrarily take it away from you. What I think you are trying to argue is related more to the fact that copyright is not an intrinsic right. As a society, we do not have to grant a copyright at all if it is not beneficial to us. We need to do a better job of balancing the interests of all parties.