What you're forgetting is that the artist's *right* is not a natural right, it's one created by society for the purpose of benefiting society.
To the extent that it does benefit society, then those *rights* represent good law. To the extent that those rights start to harm society, then those *rights* will be rescinded.
The same is true of patent law. We the people through our laws grant inventors some *rights*, but they're not on par with the right to assembly, the right free speech the right to be free from unjust imprisonment. They're *rights* that are granted solely for the purpose of incentivizing a certain kind of activity.
If an artist or other creator wants to retain perpetual and sole authority over his works, then the artist can keep them to his or her self. Beyond that, it becomes a matter of public policy who gets to use what in what fashion.
The problem with your argument is that it was a form of assuming the consequent. You assume a conclusion to the argument and use that assumption as if itself were a valid argument. You assumed that artists get to impose restrictions on other people's behavior because the artist took the step of exposing the art to the larger society. But that's a conclusion, not an argument. It's just your point of view on the matter, and not a reason why your point of view is valid.