The debate is mute, almost instantly.
The Screenwriter provides the written material, which is then created by the Director. At no point does the former posess, or is considered within the "Filming" aspect.Only when the Screenwriter has chosen to direct, or requested to consult by the Director.
Even so, the Director creates the film, and the Writer the material.
The arguement is of a power-struggle, that goes against the trust and relationship that is required when building a crew, which in this instance, is that of the Screenwriter and Director.
You will find that many Directors, when recieving merit for their films, will pay, and refer to the Screenwriter with the utmost respect, and sheer equality for the making of the story.
They're two seperate professions, even though there are thousands who do both, is still not substancial enough to raise this arguement from its death.
It's a matter of respect.
If i'm to move home, to be replaced by another owner. Whose home is it now? Mine, for i lived for twenty years, i painted the walls, i raised a family?
Or the new owners who will settle and thrive, will paint the walls, raise a family.
Where is the important, deciding factor?
The agreement, and the understanding between myself, and the new owner. The very same agreement between the Screenwriter, and Director.
It's often the case to ignore details to muster an arguement for the mere sake of debate...