I would like to attempt a non-biased response to this question. Sometimes that is challenging since I have noticed that if anything is perceived by mormons as against their position they immediately assume it is persecution but here goes.
I had no issue with the mormon church so long as they were a church. A church has the right to create it's doctrine and dogma and the members of a church have the right to believe, practice, share and enjoy their dogma. this goes for any church - mormon, catholic, jehovah's witness etc. My concern is when a church attempts to enforce their dogma on those who choose not to be a member of their church. It is a fact that the mormon church spent nearly $180,000 on passage of prop 8. that is based on their own filings with the state of california (see attached link). furthermore, it is a fact that a letter from the highest level of church leadership, known as the first presidency, wrote a letter read from the pulpit encouraging members to support passage of prop 8 with their means and time - (see attached link from the LDS website). These are facts (unless the church is lying) and they represent a formalized effort of the church at attempting to force their dogma, morals and value system on non-members of their church. now i know the mormons reading this will now be in a huff saying that i am attacking their church. the reality is, in my opinion, that everyone was getting along fine until the mormon church spent $180,000 and read a letter from the pulpit encouraging political involvement. those two acts changed the playing field. they were direct attacks on the glbt community and therefore there should not be a surprise on the part of church members, when this attack is countered.
now -for the question about the movie - why wouldn't it be allowed? many have stated already that our nation is one of guaranteed free speech. The film has not yet been released so how can the mormons on here be claiming what they are when they haven't seen it yet. You can't make the claims of persecution and false information until you actually see the movie. We know the facts are that the church clearly supported passage of prop 8. It will be interesting to see what other facts are shown in the film. The church exercised their right to support passage, both directly and indirectly, now it's time to learn more about what that support entailed.