A Screenwriter's Questions

Jim Uhls, in his screenwriting blog, raises interesting questions.

OUR ENEMIES?
Okay, I keep trying to pinpoint who exactly are the enemies of screenwriters. I won’t let the easy answers of “director,” “producer,” “studio exec” take the hit.
So, who the hell will I allow to be named as the enemies of screenwriters?
Fine. I’ll tell you.
-- And they are, above all other professions, the truly damnable cold, ruthless, reptilian marauders.
They are:
"SCREENWRITERS”
What the hell am I saying?
I’m saying -- we’ve all seen the enemies -- and they are --
-- US.
Yes, we all leap at the opportunity to wound and kill each other.
It’s called -- “being hired to rewrite a script.”
There may be millions of reasons why a writer turns down a rewrite gig.
But never in the history of film has there ever been -- or will there ever be -- a writer -- who needs the money -- or who loves the concept but dislikes the existing script -- who turns down the job because it would be morally wrong for a writer to rewrite another writer’s script.
Where else does this “artist replacement” happen? Were there playwrights called in to do a “character pass” on Tennessee William’s “A Streetcar Named Desire?”
How about painters called in to do a “polish” on the work of Michelangelo on the ceiling of the Sistine Chapel?
Or, say, “gag men” brought into to “punch up ”Shakespeare’s comedies? And maybe a writer brought in to give more depth and texture to “Hamlet?”
What about a fiction writer, brought in to give some more “pizzazz” to “The Grapes of Wrath?” or “One Hundred Years of Solitude?”
Interestingly enough, not only did these things NOT happen -- the very concept of them happening is from ANOTHER PLANET.

In an industry in which writers are routinely rewritten, can it be said that they are artists? Doesn't Hollywood's rewriting practice guarantee hackery? Would Howard Roark work in such a profession?