No films have ever been marketed with a promise to make them immutable. If they actually advertised the movie as an uneditable inmutable work of art that they promise never to alter, you *might* have an argument, but that's not the case.
The case is that the artist in this case owns his work, and he can do as he pleases. There is no law that in our current system that forces him to release his material in a version to your or my liking. In our capitalist system, this is driven by market forces, and it just so happens that most people don't really mind the changes and are going to buy whatever version is available.
I don't mind people wanting the original versions, I can respect that. But to actually entertain the idea of suing the creator and owner of the work with a class action lawsuit is the height of arrogance and stupidity. If you are really thinking about this as a serious idea, you need to take a little break and really analyse what the heck is going on wrong in your life that would have made you entertain this as a realistic course of action.