The church leaders claim that the film is offensive to Christianity and have attacked the festival itself as well as Smith.
According to Star Pulse, they released a press release branding Smith "a hater of Biblical proportions", as well as criticising Sundance founder Robert Redford for "enabling perverts".
In response to the Westboro Baptist Church's decision to picket, Smith has announced that he will stage his own protest against them at the event.
The film's plot is strongly satirical about Christian fundamentalism and radical fringe religions.
Red State will show at Sundance tomorrow, following which an official release date will be announced.