More than any other medium (except perhaps video games) film is a collaborative work. Someone needs to run the cameras, someone needs to build the sets, someone needs to write the script, someone needs to act it all out, and someone needs to direct it all. And after all that's done, someone needs to edit it into a coherent whole. A script that doesn't make it through final editing intact isn't a bad one, nor is it necessarily butchered -- but like any form of art, film is an iterative process. Things will change and grow, for one reason or another. Screenwriters like any other artist don't get to dictate how other people respond to their art, be they the general public, or the people who take those screenplays and build films out of it.