Movie purism is a general set of beliefs held by a group of fans known as Star Wars purists. These beliefs are generally that the original Star Wars films are superior to the newer ones. They tend to believe that the new Special Edition movies released in 1997, to some extent, ruined the originals. Many more narrow movie purists may also completely ignore or hate the Prequel Trilogy because they believed it destroyed the original Star Wars legacy. Most also ignore the Expanded Universe. Many film purists are also Lucas bashers.
Movie purists almost always reference the original Star Wars films released in 1977, 1980, and 1983 as being the best ever made. They tend to disagree with George Lucas' changes to the original trilogy. Among these disagreements are with the change to the "Han shot first" scene, where Han Solo shoots Greedo first in the original version of Star Wars Episode IV: A New Hope, whereas in the edited version they shoot at the same time.
Another heavy disagreement is with the replacement of Sebastian Shaw in the ghost scene of Star Wars Episode VI: Return of the Jedi with Hayden Christensen, who played Anakin Skywalker in Episodes II and III. This disagreement may be because they feel Shaw was the more accurate character to represent the ghost of Anakin, because of emotional memories, or perhaps they simply hate the Prequels.
A huge problem many film purists have with the Prequel trilogy is the concept of midi-chlorians. They believe that the Classic Trilogy created a mythology, while introducing a biological explanation for the Force, to the purists, destroys that mystical idea of there being an all-powerful Force controlling everyone's destinies.